integrate sin(2x)
Let's integrate: ∫(sin(2x))dx
We attempt to reverse an integration: starting from sin(2x) and (cos(a))' = -sin(a), we differentiate using cos
Let's differentiate: (cos(2x))'
We differentiate using: (cos(f))' = -(f)'·sin(f) (where f = 2x)
-(2x)'·sin(2x)
-2·sin(2x)
The computed derivative matches the original math expression up to a constant factor. Therefore, the integral is:
1-2·cos(2x)
-12·cos(2x)
-cos(2x)2
Indefinite integrals are defined up to an additive constant C, so this yields: -cos(2x)2 + C
Answer:   -cos(2x)2 + C, with C being any constant