Question

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.

Answer 1

Problem One
Sin(90 + q) = sin(90)*cos(q) + sin(q)*cos(90)
sin(90 + q) = 1 * cos(q) + sin(q)*0
sin(90 + q) = cos(q)

You can elimate anything beginning with Cos
You can also eliminate the sin function with a minus between it. 

Problem 2
Sin(x) = 1/csc(x) That makes C and D incorrect.
Correct answer has to be A. Since this is a multiple choice question you can't qualify the answer, but there are some points that exhibit questionable behavior, like 2 $\pi$ *f*t = 0 for example. The function becomes undefined. 

Answer 2

Answer:

the correct answer is D

Step-by-step explanation:

just got it right on edge2020