A student plans to evaluate by letting

MATHEMATICS · Single correct · CBSE · Mathematics · Integrals · Integrals

Problem

A student plans to evaluate

\displaystyle\int \cos(7x)\,dx

by letting

u = 7x

. Which of the following substitutions for

dx

is correct? (a)

dx = 7\,du

(b)

dx = \dfrac{du}{7}

(c)

dx = du

(d)

dx = \dfrac{du}{49}