Question

An equation of the line tangent to y=sin x + 2cosx at (pi/2, 1) is?

Answer 1

Answer:

B.   2x + y = pi + 1.

Step-by-step explanation:

y = sin x + 2 cos x

The slope of a line tangent is the derivative, so:

y' =  cos x - 2 sin x

At  (pi/2, 1) , substituting for x:-

cos pi/2 - 2 sin pi/2

= 0 - 2 * 1 = -2.

So the slope is - 2 and an equation  can be found by using the point-slope formula:

y - y1 = m(x - x1) so:

y - 1 = -2(x - pi/2)

y = -2x + pi + 1  

2x + y = pi + 1.