Question

Solve the equation: cos² θ = $\frac{3}{4}$, θ ∈[0, π]

Answer 1

To solve the equation: cos² θ = $\frac{3}{4}$, θ ∈[0, π]

take square root both sides
$cos \: \theta = \sqrt{ \frac{3}{4} } \\ \\ cos \: \theta = \frac{ \sqrt{3} }{2}$

So

$\theta = {cos}^{ - 1} ( \frac{ \sqrt{3} }{2} ) \\ \\\theta = {cos}^{ - 1} (cos \: ( \frac{\pi}{6} ) \\ \\\theta = \frac{\pi}{6}$

is the solution of the equation.