Let us assume .....equation 1

By property, we know that

.......equation 2

Adding equation 1 and equation 2

We know

……equation 3

Let cosx = y

Differentiating both sides

– sinxdx = dy

sinxdx = – dy

for x = 0

cos0 = y

1 = y

For x = π

cosπ = y

– 1 = y

Substituting equation 3 becomes

2I = 2π/5

I = π/5