Question

-2cos 3(t-pi/2)

Answer 1

\[t=\frac{ \pi }{ 2 }\]

Answer 2

we have to find the root of this equation?

Answer 3

i think you should expand the brackets first
After you expand the cos part of it using
\[\cos (A + B) = \cos A \cos B - \sin A \sin B\] OR
\[\cos (A - B) = \cos A \cos B + \sin A \sin B\]