+0

# Precalc anyone?

+1
259
4
+478

Okay, I don't even know where to start on this question. Hints (not full solution would be helpful :D )

Find all possible values of $$cos(\theta)$$ if $$cos(2\theta) = 2cos(\theta)$$.

Oct 22, 2021

### 4+0 Answers

#1
-1

$\cos \theta = \frac{3}{4}$

Oct 22, 2021
#2
+2402
+1

cos(2x) = 2cos^2(x) - 1

cos(2x) = 2cos(x)

2cos^2(x) - 1 = 2cos(x)

Any idea on what to do from here?

=^._.^=

Oct 23, 2021
#3
+488
0

quadratic in terms of cos(x)?

textot  Oct 23, 2021
#4
+117494
+1

You got it

Thanks catmg

Melody  Oct 23, 2021