Question

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Answer 1

\[
\cos(\pi/2)=0\\
\sin(\pi/2)=1
\]
Don't think too much.

Answer 2

\[
\pi/2=90\text{ deg}
\]

Answer 3

but what about the extra pi/2 that is standing in there alone?

Answer 4

It is multiplied by \(\cos(\pi/2)=0\)

Answer 5

oh pi/2 is multiplied with cospi/2

Answer 6

thanks

Answer 7

\[
\frac{\pi}{2}\cos(\pi/2)=\frac{\pi}{2}\times 0=0
\]