Question

Help this is my homework I been struggling and I can not find the mistake I will appreciate it!

Answer 1

The formula for the sum of angles in cosine is:

`\cos (a+b)=\cos (a)\cdot\cos (b)-\sin (a)\cdot\sin (b)`

So in this case the error is adding instead of substracting.

Let's correct it:

`\cos (x+(3\pi)/(2))=\cos (x)\cos ((3\pi)/(2))-\sin (x)\sin ((3\pi)/(2))`

`\cos (x+(3\pi)/(2))=\cos (x)\cdot0-\sin (x)\cdot-1`

`\cos (x+(3\pi)/(2))=\sin (x)`