Question

Find the equation of the line tangent to the graph of y = cos(2x) at x = pi/4

Answer 1

at x=pi/4, y=0

find the derivative
y'=-2sin2x

sub pi/4 to y'
y'=-2 which is the slope of the line

Thus, the equation of the tangent is y=-2x+b, sub in values to find b

In the end, the equation you should get is y=-2x+pi/2

Answer 2

What values do I put in to find b?

Answer 3

I got -2 + 0

Answer 4

use x=pi/4 and y=0