Question

If cos2theta = 1/3 and 0 ≤ theta ≤ pi/2, find costheta.

Answer 1

\[\cos^2(\theta) or \cos(2\theta)\]?

Answer 2

Cos(2theta) = 2 cos^2 theta -1

Answer 3

cos(2θ)

Answer 4

use a calculator enter:
\[\cos(\frac{\cos^{-1}(1/3)}{2})\]

Answer 5

.816 radians

Answer 6

If u are expected to provide an exact value use the equation I gave above.

Answer 7

yeah i needed the exact value, thanks

so you do 2cos^2theta - 1 = 1/3
and solve for costheta, got it