Question

What is the integration of cos3x​

Answer 1

Explanation:

Integral of cos3x = ⅓sin3x

So when integrating just simply multiply by reciprocal of the cooeffecient of the angle and the integral of that particular trig ratio, in this case it's the sinx.

Answer 2

1/3 sin(3x)+C

Explanation:

int (cos(3x) dx)

Let u=3x then du=3 dx so 1/3 du=dx

rewriting integral

int(1/3 cos(u) du)

now evaluating

1/3 sin(u)+C since (sin(u))'=cos(u)

Replace u with 3x

Answer is 1/3 sin(3x)+C