Trig and Caclulus Together?

Question

Verify equation is an identity.

cos(pie/2 + x) = -sinx

Find the local extrema of f

x^2/3(x-7)^2 + 2

Answer 1

For the first one -- come on, you surely know the formula for cos(a+b).

For the second, differentiate. The Quotient Rule is your friend, but in this special case it would be a shortcut to differentiate (x/(x-7))^2 using the Chain Rule, and maybe even to write x/(x-7) as 1 + 7/(x-7).