Math (trigonometric identities)
posted by Kim .
I was given 21 questions for homework and I can't get the last few no matter how hard and how many times I try.
17. Sinx1/sinx+1 = cos^2x/(sinx+1)^2
18. Sin^4x + 2sin^2xcos^2x + cos^4x = 1
19. 4/cos^2x  5 = 4tan^2x  1
20. Cosx  sinx  cos^3x/Cosx = sin^2  tanx
21. Sin^2x  6sinx + 9/sin^2x  9 = sinx3/sinx+3
Especially the last three!

Math (trigonometric identities) 
Mac
19). 4sin^2x/cos^2x  cos^2x/cos^2x
4(1cos^2x)  cos^2x. All over cos^2x
4  4cos^2x  cos^2x. All over cos^2x
4  5cos^2x. All over cos^2x
4/cos^2x  5 
Math (trigonometric identities) 
Mac
20). Sin^2x  sin x / cos x
(1cos^2x)cos x  sin x. All over cos x
Cos x  cos^3x  sin x. All over cos x 
Math (trigonometric identities) 
Mac
21). Factor the numerator and the denominator
(Sin x  3)(sin x  3) / (sin x  3)(sin x + 3) 
Math (trigonometric identities) 
Mac
17). Multiply numerator and denominator by
Sin x + 1
The numerator ( sin x + 1)(sin x 1) = sin ^2x 1
= 1(1  sin^2x) = cos^2x 
Math (trigonometric identities) 
Mac
18). Factor perfect square ( sin ^2x + cos^2x)^2
= 1^2=1
Respond to this Question
Similar Questions

Simplifying with Trigonometry Identities
Hi, I am a senior in High School having a really difficult time with two problems. I have to prove using the trigonometric identities that they equal each other but I am having a really hard time trying to get them to equal each other. … 
Trigonometry.
( tanx/1cotx )+ (cotx/1tanx)= (1+secxcscx) Good one! Generally these are done by changing everything to sines and cosines, unless you see some obvious identities. Also generally, it is best to start with the more complicated side … 
Mathematics  Trigonometric Identities
Prove: sin^2x  sin^4x = cos^2x  cos^4x What I have, LS = (sinx  sin^2x) (sinx + sin^2x) = (sinx  1 cos^2x) (sinx + 1  cos^2x) = sin^2x + sinx  sinx  cos^2xsinx  cos^2xsinx  1  1 + cos^4x = sin^2x  2cos^2xsinx  2 + cos^4x … 
Mathematics  Trigonometric Identities  Reiny
Mathematics  Trigonometric Identities  Reiny, Friday, November 9, 2007 at 10:30pm (sinx  1 cos^2x) (sinx + 1  cos^2x) should have been (sinx  1 + cos^2x) (sinx + 1  cos^2x) and then the next line should be sin^2x + sinx  cos^2xsinx … 
Trig
Simplify sin x cos^2xsinx Here's my book's explanation which I don't totally follow sin x cos^2xsinx=sinx(cos^2x1) =sinx(1cos^2x) =sinx(sin^2x) (Where does sine come from and what happend to cosine? 
Trig Help
Prove the following: [1+sinx]/[1+cscx]=tanx/secx =[1+sinx]/[1+1/sinx] =[1+sinx]/[(sinx+1)/sinx] =[1+sinx]*[sinx/(sinx+1)] =[sinx+sin^2x]/[sinx+1] =[sinx+(1cos^2x)]/[sinx+1] =? 
Math
1) evaluate without a calculator: a)sin(3.14/4) b) cos(3(3.14)/4) c) tan(4(3.14)/3) d) arccos( square root of three/2) e) csctheata=2 2) verify the following identities: a) cotxcosx+sinx=cscx b)[(1+sinx)/ cosx] + [cosx/ (1+sinx)]= … 
Trigonometry
Prove the following trigonometric identities. please give a detailed answer because I don't understand this at all. a. sin(x)tan(x)=cos(x)/cot^2 (x) b. (1+tanx)^2=sec^2 (x)+2tan(x) c. 1/sin(x) + 1/cos(x) = (cosx+sinx)(secx)(cscx) d. … 
Math Help
Hello! Can someone please check and see if I did this right? 
Math
I need help solving for all solutions for this problem: cos 2x+ sin x= 0 I substituted cos 2x for cos^2xsin^2x So it became cos^2(x)sin^2(x) +sinx=0 Then i did 1sin^2(x)sin^2(x)+sinx=0 = 12sin^2(x)+sinx=0 = sinx(2sinx+1)=1 What …