Which Dr Du class are you in?
a) Okay with this question we are required to find the auxiliary angle which is in the form
)
for
Well,
 = R\sin{x}\cos{\alpha}+R\cos{x}\sin{\alpha})
where
Now, put

and

side by side what do you see.

noting the condition

noting the condition

. Putting it together we will have
)
.
b) Now we have to sketch
)
in the range of

.
Hint: Compare this to the original function

and note the differences. Then sketch this character.
That is only the first question. I imagine the later question will be harder than this one I presume. Anyways
@Farhanthestudent005 just send them here. We are waiting for them.