ex sin(x) is a product of two functions: ex and sin(x). This means we can use the product rule.
Let ex = u and sin(x) = v
The differential of uv is u'v + v'u where u' and v' are the two functions differentiated separately.
u' = ex and v' = cos(x)
So the differential of exsin(x) is exsin(x) + excos(x)