Question

For how many values of x will the tangent lines to y=4sinx and y=x^2/2 be parallel?
A. 0
B. 1
C. 3
D. 4
E. Infinite

Thanks.

Answer 1

we want the slopes to be equal

4cosx = x

That occurs only 3 places.

See

http://www.wolframalpha.com/input/?i=x+%3D+4cosx