# What is the integral of cos 2x?

What is the integral of cos 2x?

Solution: Using integration by substitution.

Put 2x = u, so 2dx = du or dx = (1/2) du

Now,

$$\begin{array}{l}\int cos \ 2x dx = \int cos \ u (1/2) du\end{array}$$

= (1/2)(sin u) + c

= (1/2) sin(2x) + c

= (1/2)(sin 2x) + c

Where c = constant of integration.

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