Urgent! two questions! (pre calc) (30 points)

1)which sum or difference identity would you use to verify that sin (90° + q) = cos q?

a. cos (a -b) = cos a cos b + sin a sin b
b. sin (a +b) = sin a cos b + cos a sin b
c. sin (a -b) = sin a cos b- cos a sin b
d. cos (a +b) = cos a cos b - sin a sin b

2) when an alternating current of frequency (f) and a peak current (i) passes through a resistance (r), then the power delivered to the resistance at a time (t) seconds is p=(i^2)(r)(sin^2)(pi)(ft).
write an expression for the power in terms of (csc^2)(2)(pi)(ft).

see image attached for options a, b, c and d and actual question 2.