# Prove the identity cos3x ≡ 4cos^3x - 3cosx Thank you so much for the help!

4,977 results
1. ## Optional mathematics

Prove that (3-4sin^2A) (1-3Tan^2A)= (3-tan^2A) (4cos^2A-3)

asked by Alina maharjan on July 14, 2017
2. ## maths

Prove that (2√3+3)sinx+2√3cosx lies between -(2√3+15) and (2√3+15)

asked by krishan on June 18, 2012

pls. help: prove the identity sin2x+sin2y=2sin(x+y)cos(x-y)

asked by justme on November 29, 2011
4. ## Math - Trig - Double Angles

Prove: cos4x = 8cos^4x - 8cos^2x + 1 My Attempt: RS: = 4cos^2x (2cos^2x - 1) + 1 = 4 cos^2x (cos2x) + 1 LS: = cos2(2x) = 2cos^2(2x) - 1 = (cos^2(2)) - cos^2(2x)) - 1 ----- Prove: 8cos^4x = cos4x + 4cos2x + 3 My Attempt: RS: = cos2(2x) + 4cos(2x) + 3 =

asked by Anonymous on November 17, 2007
5. ## Calculus

Sketch the region enclosed by the curves given below. Decide whether to integrate with respect to x or y. Then find the area of the region. y=4cos(x),y=4−8x/π. I thought it was the integral of 4cos(x)- the integral of 4- 8x/π on the interval 0 to π/2.

asked by Kevin on April 27, 2016
6. ## calculus - identities

prove this identity: sec(y) - cos(y)= tan(y)sin(y) THANK YOU!!

asked by Amber on October 16, 2009
7. ## Trigonometry

Verify Identity: cos5x-cos3x=-8sin^2x(2cos^3x-cosx)

asked by Erik on July 2, 2011
8. ## trig

asked by Anonymous on February 22, 2013
9. ## precalc

prove the identity : cos3x =4 cos^3x-3cosx

asked by Anonymous on March 6, 2018
10. ## precalc

use power reducing identities to prove the identity sin^4x=1/8(3-4cos2x+cos4x) cos^3x=(1/2cosx) (1+cos2x) thanks :)

asked by skye on August 16, 2012
11. ## Pre-Calc/Math

Prove Identity: (1-cos2x/ tan x) = sin2x

12. ## Math

a) prove the identity: Ax(BXC)=B(A*C)-C(A*B) A,B,C vectors x- cross product *-dot product b) use part a) to prove that cross product is not associative.

asked by larry on October 31, 2014
13. ## maths

prove that cos3x+sin3x/cos x-sin x=1+2sin2x

asked by sunny on July 22, 2009
14. ## Math

Prove the identity: sec^4x - tan^4x = 1+2tan^2x

asked by Shane on November 10, 2014
15. ## Calc III

Express the volume of the solid that the cylinder r = 4cos(theta) cuts out of the sphere of radius 4 centered at the origin with a triple integral in cylindrical coordinates. I have already found the intervals, but I cannot solve it. The bounds are

asked by Anon on November 2, 2016
16. ## Math

Prove the identity cos3x ≡ 4cos^3x - 3cosx Thank you so much for the help!

asked by Autumn on December 6, 2018
17. ## trig

By expressing 3x as (2x + x) prove that cos3x = 4cos^3x - 3cosx

asked by Rin on December 13, 2011
18. ## Pre Calculus

Prove that 2/square root 3cosx-sinx=sec(pi/6-x)

asked by Nathan on April 22, 2010
19. ## Trig

prove the identity (sinX)^6 +(cosX)^6= 1 - 3(sinX)^2 (cosX)^2 sinX^6= sinx^2 ^3 = (1-cosX^2)^3 = (1-2CosX^2 + cos^4) (1-cosX^2) then multiply that out 1-2CosX^2 + cos^4 - cosX^2 + 2cos^4 -cos^6 add that on the left to the cos^6, and combine terms..

asked by JungJung on December 8, 2006
20. ## Maths

Prove that cos3x/cosx-cos6x/cos2x=2(cos2x-cos4x)

asked by Joel on July 28, 2016
21. ## Trig

Prove the following functions: (sinx+sin2x)/(1+cosx+cos2x)=tan x (cos3x/sinx)+(sin3x/cosx)=2cot2x tan2x=(2/cotx-tanx) theses are due in the am. Fastness would be great?

asked by jared on November 7, 2011
22. ## Algebra

Question : Determine whether each of the following given sets is a group with respect to the indicated operation. Show your work. (b) The set E of all even integers with operation addition. My work : So I was working on above part (b) Following is an

asked by Ashley on May 9, 2020
23. ## Trigonometry

Prove it is an identity. (sin^2x)/(tanx)=sinxcosx

asked by . on April 19, 2010
24. ## Maths

Prove that the identity element e of a group G is unique.

asked by Santosh on July 30, 2011
25. ## Precalculus with Trigonometry

Prove or disprove the following identity: cos (x+pi/6) +sin (x-pi/3) = 0

asked by Natalie on April 7, 2013
26. ## Calculus

Prove the identity and give its domain. 4sinxcosx+sin4x=8sinxcos^3x

asked by Courtney on February 6, 2008
27. ## trig

By expressing 3x as (2x + x) prove that cos3x = 4cos^3x - 3cosx

asked by Rin on December 13, 2011
28. ## maths...

Differentiate ln [x+√(x^2+1)] with respect to x hence evaluate limit 0 to 1 ∫ 1/√(x^2+1) dx _________________________________________ Use the identity cos3x=4cos^3x-3cosx, find ∫cos^3x dx * Is there a printing error in the question? the limit is

asked by Aoi on June 19, 2009
29. ## maths

find the value of x if sin2x+3cosx=2 then cos3x+sec3x is

asked by rajagopal on September 6, 2017
30. ## trig

how do you verify cos3x=4cos^3x-cosx???

asked by lindsey edler on July 12, 2005
31. ## math

Prove the identity: cos^4(x)-sin^4(x)=1-2sin^2(x).with explanation im confused on this one cause of the 4th power of the sine. does this mean that we put it in the calculator 4 times? and what exactly does it mean by prove the identity- does it mean like

asked by Anonymous on April 15, 2012
32. ## pre-cal

find all solutions in interval [0,2pi] tan²x = -3/2 secx This question may look tricky, but its actually quite simple. First: rearrange the pythagorean identity tan²x+1=sin²x so that it reads tan²x=sin²x-1 Then replace the tan²x in the original

asked by ethan on May 16, 2007
33. ## Trig

verify the following identity: 2sinxcos^3x+2sin^3cosx=sin(2x)

asked by Lynn on July 19, 2012
34. ## trigonometry

Prove: sin3x-sinx/cos3x-cosx=-cot2

asked by Dini on November 2, 2010
35. ## trig--power reducing formulas

Having trouble with this problem: Rewrite the expression as an equivalent expression that does not contain powers greater than 1. Cos³x My answer: cos³x=(cos²x)(cosx) =(1+cos2x/2)(cosx)-->cos+cos³x/2...which is wrong

asked by Brian on April 20, 2009

for each function, determine the equation of the tangent line to the graph for the indicated value of the variable. a) y = 3cosx + 4sinx + 1 , when x = pie b) y = x - 3cosx , when x = (5pie)/3

asked by stephanie on June 21, 2012

Prove this identity using the product-to-sum identity for sine: sin^2 x=1-cos(2x)/2

asked by Kyle on April 5, 2016
38. ## Math

Prove That Cos3A = 4Cos A - 3Cos A

39. ## TRIG

Verify the following identity. 1) sin(x+y) __________ = tanx+tany cosxcosy 2) Write cos3x in terms of cosx I cannot figure out how to solve for identities they are so hard. Any help appreciated!:)

asked by ALISON on October 23, 2011
40. ## trig

sin^4 x = (3-4cos 2x + cos4x)/8 prove on one side please!

asked by Rachel on February 23, 2009
41. ## math

Prove that:(3-4sin^2A) (1-3tan^2A)=(3-tan^2A)(4cos^2A-3)

asked by Rishabh on October 13, 2014
42. ## Trig

Prove (cos^2t+4cos^2+4)/(cost+2)=2sect+1)/sect

asked by Katie on March 3, 2012
43. ## Math

Select all the true statements about identities. A) You may use proven identities to prove other identities. B) An identity is true only for restricted values of the variables. C) You can prove an identity by graphing the side to the left of the equal

asked by TeeKay on October 14, 2014
44. ## trig

prove that the equation 2sin x cos x +4cos^2 x =1 may be written in the form of tan^2 x -2tan x -3=0

asked by Nus on January 3, 2015
45. ## CALC

I did post it wrong. sin(4x)/sin(x)=4cos(x)cos(2x). Verify the identity, please explain!

asked by JD on August 13, 2011
46. ## calc

sin(4x)/sin(x)=4cos(x)cos(x) verify the identity

asked by jessica on August 13, 2011
47. ## Trigonometry

Need help solving problems using the Trigonometric Identities: 8cos^4 thet=cos4theta+4cos2theta+3 I am a bit unsure how to solve it. I am aware that the first step I must take is to simplify the problem and then use the Product to Sum formula Nasty one!

asked by sierra on April 23, 2007
48. ## Child Development

Rachel is a highechool student who has explored several employment and education alternatives. She has chosen to attend the community college near home to become a diesel mechanic. What is the identity status of Rachel according to James Marcia? A.

asked by Jessica on May 20, 2014
49. ## Math - Trigonometry

In order to prevent confusion that may be caused by reading this problem written through keyboard text, I have written the identity in microsoft paint here: gyazo. com/3afe07a6067e467d3776dd8b64ccac91 I need to find three different ways (Different meaning

asked by Monika on March 15, 2018
50. ## Math - Trigonomotry

Hello! In order to prevent confusion that may be caused by reading this problem written through keyboard text, I have written the identity in microsoft paint here: gyazo. com/d4529f091e5ba75c09a9a283201504d2 I need to find three different ways (Different

asked by Monika on March 14, 2018
51. ## algebra

Give am example of a function f.N N with the property that there exists a function g. N N such that the composition got is the identity function on N but for no function h. N N does it hold that fog is the identity function on N.Prove all claims

asked by geeta on February 27, 2014
52. ## math

1. Prove the identity:cosx/1-tanx+sinx/1-cotx=sinx+cosx 2.Prove the identity: cosx/1+sinx+1+sinx/cosx=2secx

asked by Aliya on August 20, 2011
53. ## trig

Write an equation for simple harmonic motion, given that the amplitude equals 4 inches and the period equals 2 seconds and the max displacement occurs when t=0. answers: y=4sin pi t, y=4cos pi t, y=4cos t, y=4sin2 pi t

asked by Kayla on May 17, 2012
54. ## English

Hi I am writting an essay on a book called 'Funny Boy' I have to answer this question: Selvadurai raises questions about the nature of identity—national, familial, sexual, postcolonial, ethnic, racial—and how the suppression of one’s burgeoning or

asked by Mary on March 31, 2010
55. ## circular (trigonometric) functions

hi, i need help solving this trigonometric equation: sinx+3cosx=0 i don't know what to do as i can't just diviide the two to create tanx which is what i have been doing in previous questions... yes, you are on the right track sinx = -3cosx sinx/cosx = -3

asked by elle on April 14, 2007
56. ## trig

cos(sin^-1 x)=sq rt(1-x^2) prove the identity

asked by Emily on April 2, 2012
57. ## Pre-Calculus

Prove the identity: cos(x-π/2)=sin x

58. ## Trigonometry

Prove the identity sin(x+y+z)+sin(x+y-z)+sin(x-y+z)+ sin(x-y-z) = 4 sin(x)cos(y)cos(z) This identity is so long and after i tried to expand the left side and it just looked something crap Thanks for you help :)

asked by Tommy on July 19, 2008
59. ## Math pre cal

prove the following identity cos^4X - sin^4X = 1-2sin^2X

asked by Breanna on September 28, 2009
60. ## Pre-Calc !!!

Prove the identity. 2tanx/1+tan^2x=sin^2x

asked by Josh on April 16, 2012
61. ## Math

How do you prove this identity? cos2x*tan(π\4-x)= 1-sin2x

asked by Branco on February 5, 2020
62. ## math

Prove the identity (sinx+cosx)^2 = 1+sin2x Thank you

asked by Bear on January 28, 2015
63. ## Prove trig identity

Prove the following trigonometric identity: (sec^2x-1)(csc^2x-1)=1

asked by Randy on January 9, 2011
64. ## math

asked by John on March 1, 2010
65. ## trig

sinx+sinxcot^2x=cscx prove each identity

asked by tom on June 24, 2011
66. ## MATH

prove the identity: cos(x)*csc(x)*tan(x)=1

asked by Alisa on November 6, 2014
67. ## math

asked by John on March 1, 2010
68. ## Trigonometry

Prove the identity. 6cos^2(x)-1 -12cos^4(x) +8cos^6(x)= cos^3(2x) Thanks for your help :)

asked by Tommy on July 18, 2008
69. ## Math

prove the identity: sin^2 O/ 1-cos O = 1+cosO O= theta

asked by amber on April 27, 2012
70. ## Math

Prove the identity: cosx/1-tanx +sinx/1-cotx

asked by Aliya on August 20, 2011
71. ## precalc

prove the identity (1 + tan x) / sin x = csc x + sec x

asked by clarice on October 13, 2015
72. ## PreCalculus

Prove the following to be an identity (cotx + cscx)*(1-cosx)=sin x

asked by Kevin on October 15, 2017
73. ## Calculus

prove if an identity csc (x)-cot (x)=sin (x)/1+cos(x)

asked by Anonymous on October 15, 2018
74. ## pre calc

prove identity cscx-(cosx)(cotx)=sinx

asked by logan on November 29, 2010
75. ## Math

asked by Kristien on February 23, 2013
76. ## Math

Required to Prove the following trig identity: (cos2x)^2 + (sin2x)^2 = 1

asked by Halle on June 18, 2009
77. ## math trigonometry

Prove the identity Sin^3X sinx*cos^2X=tanx/cosX

asked by happy on June 9, 2015
78. ## math trigonometry

Prove the identity Sin^3X+sinx*cos^2X=tanx/cosX

asked by happy on June 9, 2015
79. ## trig

Prove the identity. (must work with left side) (1-2sin(x)^2)=(cos(x)^2)

asked by mailon on September 4, 2008
80. ## math

prove the following trigonometric identity: (cos x/(1+sinx))+tanx = secx

asked by Liz on March 12, 2008
81. ## Pre-Calc/Math

Prove identity: (sec x/csc x) + (sin x/cos x)=(2/cot x)

82. ## math

sinx+ siny/ (cosx+cosy)= tan 1/2 (x+y) prove this identity

asked by JK on August 13, 2010
83. ## math

prove the identity cos x/sec x-tan x=1plus sin x

asked by laston on December 13, 2016
84. ## gr 12. advanced functions

Trig identity Prove: cos2x tan(pie/4 - x) ------- = 1 + sin2x

asked by avm on November 21, 2009
85. ## Math

Prove the identity csc^2x = 2sec2x / sec2x - 1 Sorry i really tried. I got : LS = 1 - (cos^2x/sin^2x) but that's it. please help

asked by Nihira on June 17, 2014
86. ## maths

If f(x)=x(2pi-x) in 0

asked by Rahul on September 9, 2012
87. ## Math

Prove this identity. State any restrictions on the variables. sin x/(tan x)= cos x

asked by Emily on December 9, 2010
88. ## Math (PreCalculus)

How do I prove the following identity? sec^2x-1 (division line)> -------- = (tanx)(secx) (sinx)

asked by Charli on February 3, 2015
89. ## Math (pre-celc 12)

I need to prove this identity: cot(x)+tan(x)=csc(x)sec(x) I get as adding them together, but then I get stuck.

asked by Jana on June 17, 2016
90. ## Precalculus

2-3cosx=5+3cosx 0 degrees is less than or equal to x less than or equal to 180 degrees Can you please show me step by step in detail. Please do not skip a step. Thanks!

asked by Jess on August 6, 2011
91. ## Trigonometry

For all values of x for which the expressions are defined, prove the following equation identity 2/sec = 2-2 sin^2 x/ cos x

asked by Anna on March 17, 2016
92. ## precalculus

Sin(x+y)cos(x-y)= 1/2sin2x+ 1/2 sin2y Help please I have no idea how to do this because my math class never did it but while making the final review for the chapter I was assigned, I put this one in it. They are going to all ask me how to do it.

asked by Dustin on January 15, 2015
93. ## Math- gr.12 Trig.

Hi, could someone explain to me how to use a counterexample in trig to prove whether something is either an identity or equation? For ex. how would you do that with this question? sec^2x-tan^2x= cos x

asked by May on January 11, 2010
94. ## ah trig help

use an apropriate sum or difference indentity to prove the double-angle identity cos2u=1-2sin2u

asked by amber on April 26, 2011
95. ## trig

determine wheather each of the following is an identity or not prove it 1. cos^2a+sec^2a=2+sina 2. cot^2a+cosa=sin^2a

asked by Anonymous on March 20, 2011
96. ## Math

Prove the identities 1. cos3Ɵ + cos Ɵ = 4cos^Ɵ - 2 cos Ɵ 2. sin (A+B)sin (A-B)=cos2B + sin^2 A-1

asked by Anonymous on October 25, 2012
97. ## Physics

Given below are the some of the function of x and t to represent the displacement (transverse or longitudnal ) of an elastic wave . State whether it is stationary or travelling wave or none of them. (i) y = 3sin(5x+0.5t) + 4cos(5x+0.5t) (ii) y =

asked by Raj on December 2, 2016
98. ## Pre Cal

could someone please tell me what the other angle identity of tan is? Thank you much! "...other angle identity of tan x"? in relation to which "other" ? there are many identities dealing with the tangent. The most important is probably tan x = sin x/cos x

asked by Marie on May 23, 2007
99. ## MathS triG

1 .If tanA=1/3 and tanB=1/7 (both A and B are acute),calculate 50sin(2A +B) 2.1Prove that sin2A+2cosA-2cos^3A/1+sinA =sin2A 2.2 for which values of A in the interval[-360;360] is the identity in 2.1 undefined? 3.If tanB=3/4 , 0

asked by OwamIII on April 8, 2014
100. ## maths Pls help trig

1 .If tanA=1/3 and tanB=1/7 (both A and B are acute),calculate 50sin(2A +B) 2.1Prove that sin2A+2cosA-2cos^3A/1+sinA =sin2A 2.2 for which values of A in the interval[-360;360] is the identity in 2.1 undefined? 3.If tanB=3/4 , 0

asked by tshepo on April 8, 2014