The equation is .

Differentiate on each side with respect to .

.

Part 1 of the fundamental theorem of calculus :

If  is continuous on , then the function  is defined by  is continuous on  and differentiable on , then .

Compare  with .

The function .

From the fundamental theorem of calculus, part 1 .

Therefore,

.

Find  by substituting  in .

.

The function is  and the number .