Answer:
Step-by-step explanation:
It's going to be C. 15... You can easily figure this out by using the equation 35 - 20 = x
Answer:
It's number three, I'm sure.

Step-by-step explanation:
F(x) = cos x
f'(x) = -sin x
f''(x) = -cos x
f'''(x) = sin x
f''''(x) = cos x
90/4 = 22 Remainder 2
Therefore, 90th derivative of f(x) = cos x is -cos x.