JEE Main2017MathematicsDefinite IntegrationActual
The integral ∫ π 4 3 π 4 d x 1 + cos x is equal to
Options
- A- 2
- B2
- C4
- D- 1
Correct answer
B. 2
Step-by-step solution
Let, I = ∫ π 4 3 π 4 d x 1 + cos x ⇒ I = ∫ π 4 3 π 4 d x 1 + 2 cos 2 x 2 - 1 ⇒ I = 1 2 ∫ π 4 3 π 4 sec 2 x 2   d x ⇒ I = tan x 2 π 4 3 π 4 ⇒ I = tan 3 π 8 - tan π 8 ⇒ I = 2 + 1 - 2 - 1 ⇒ I = 2 .