Question

Use the given substitution and the chain rule to find
dy/dx
y=cos (6x - 5), u = 6x-5

Answer 1

Substituting u = 6x - 5, you write

y = cos(u)

Then differentiating with the chain rule gives

dy/dx = dy/du • du/dx

We have

dy/du = -sin(u)

du/dx = 6

so

dy/dx = -6 sin(u) = -6 sin(6x - 5)