Maths  trig
posted by Rose .
Solve 3cos2x  7cosx = 0, when 0<=x<=360
And also, find the exact values for x when 0<=x<=360 if 3tan^2x=1
Thankyou!

have you come across
cos 2x = 2cos^2 x  1 ?
let's sub it.
3cos 2x  7cosx = 0
3(2cos^2 x  1)  7cosx = 0
6cos^2x  7cosx  3 = 0
(2cosx3)(3cosx+1) = 0
cosx = 3/2 , which is not possible,
or
cosx = 1/3
so x must be in quadrants II or III
angle in standard position is 7.53 , then
x = 18070.53 = 109.47°
or
x = 180+70.53 = 250.53 
3tan^2 = 1
tan^2x = 1/3
tanx = ± 1/√3
x = 30°, 150°, 210° or 330° 
3cos2x+7cosx+3=0
Respond to this Question
Similar Questions

math
Find the exact value of cos 300 degrees. thanks guys cos 300 = 1/2 = 0.500 how do you know? 
math
A and B these 2 companies are fixing a road,A fixes 62% of the road,which is 360 meters more than B fixed.How long is this road? 
Mathematics
Hi there, Can someone help me with the question: "Prove that the value of 7sinx +3cos2x cannot be greater than 5/1/24 for all values of x between 0 degrees and 360 degrees" Thanks lots. =) I've already simplified 7sinx + 3cos2x into … 
MATHEMATICS
what is the exact value of 12sin(15degrees)? 
inverse trig HELP PLEASE!!
Write the general solution to y = arcsin (0.6428). 40°±360°k 140°±360°k 220°±360°k 320°±360°k How do I find the right answer? 
Precalculus
Write the general solution to y = arcsin (0.6428). 40°±360°k 140°±360°k 220°±360°k 320°±360°k 
MathsSs triG
Consider sin(x360)sin(90x)tan(x)/cos(90+x) 1.A.SIMPLIFY sin(x360)sin(90x)tan(x)/cos(90+x) to a single trigonometric ratio B.hence or otherwise without using a calculator,solve for X if 0<X<360. sin(x360)sin(90x)tan(x)/cos(90+x) … 
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+2cosA2cos^3A/1+sinA =sin2A 2.2 for which values of A in the interval[360;360] is the identity in 2.1 undefined? 
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+2cosA2cos^3A/1+sinA =sin2A 2.2 for which values of A in the interval[360;360] is the identity in 2.1 undefined? 
Math  Linear Approximation
I have a followup question from a problem I posted earlier: Approximate sin(61π/360): So, sin(60π/360 + π/360) = sin(π/6 + (π/360)) Now the equation for linear approximation is f(x+a)=f(a)+f'(a)(xa). To get the right answer, …