Evaluate the following integrals:
∫ x3 sin x4 dx
Assume x4 = t
d(x4) = dt
4x3dx = dt
x3dx = 
Substituting t and dt
⇒ 
⇒ 
But t = x4
⇒ 
.
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Evaluate the following integrals:
∫ x3 sin x4 dx
Assume x4 = t
d(x4) = dt
4x3dx = dt
x3dx =
Substituting t and dt
⇒
⇒
But t = x4
⇒ .