What is the Integral of Cos 2x

Answer: We can’t just integrate cos2(x) as it is, so we need to change it into a different form. Using trig identities is easy to do.

Remember the formula for the double angle: cos(2x) = cos2(x) – sin2 (x). We also know that sin2(x) + cos2(x) = 1, so when we put these two things together, we get cos(2x) = 2cos2(x) -1.

Now, we can switch things around to get: cos2(x) = (1+cos(2x))/2.

So, we have an equation that gives cos2(x) in a more excellent form, which we can easily integrate using the reverse chain rule.

This gives us the answer, which is x/2 + sin(2x)/4 + c