9000046504
Level:
A
Identify the optimal first step convenient to solve the following trigonometric
equation. Do not consider the step which is possible but does not help to solve the
equation.
\[
\cos \left (x + \frac{\pi }
{3}\right ) = \frac{\sqrt{3}}
{2}
\]
substitution \( x + \frac{\pi } {3} = z\)
\(\cos ^{2}\left (x + \frac{\pi } {3}\right ) = \frac{3}
{4}\)
substitution \( \frac{\sqrt{3}}
{2} = z\)
\(\cos x\cdot \cos \frac{\pi }{3} -\sin x\cdot \sin \frac{\pi }{3} = \frac{\sqrt{3}}
{2} \)