NIMCET 2013 — Mathematics PYQ
NIMCET | Mathematics | 2013The value of the integral ∫0π/2sinx+cosxsinxdx is:
Choose the correct answer:
- A.
0
- B.
−4π
- C.
2π
- D.
4π
Explanation
Solution
Step 1: Assign the integral to a variable I
Let
I=∫0π/2sinx+cosxsinxdx— (Equation 1)
Step 2: Apply the property ∫abf(x)dx=∫abf(a+b−x)dx
Here, a=0 and b=π/2. We replace x with (π/2−x):
I=∫0π/2sin(π/2−x)+cos(π/2−x)sin(π/2−x)dx
Using trigonometric identities sin(π/2−x)=cosx and cos(π/2−x)=sinx:
I=∫0π/2cosx+sinxcosxdx— (Equation 2)
Step 3: Add Equation 1 and Equation 2
I+I=∫0π/2sinx+cosxsinxdx+∫0π/2sinx+cosxcosxdx
2I=∫0π/2sinx+cosxsinx+cosxdx
Step 4: Simplify and integrate
2I=∫0π/21dx
2I=[x]0π/2
2I=2π−0
I=4π
Correct Option: 4. 4π
Explanation
Solution
Step 1: Assign the integral to a variable I
Let
I=∫0π/2sinx+cosxsinxdx— (Equation 1)
Step 2: Apply the property ∫abf(x)dx=∫abf(a+b−x)dx
Here, a=0 and b=π/2. We replace x with (π/2−x):
I=∫0π/2sin(π/2−x)+cos(π/2−x)sin(π/2−x)dx
Using trigonometric identities sin(π/2−x)=cosx and cos(π/2−x)=sinx:
I=∫0π/2cosx+sinxcosxdx— (Equation 2)
Step 3: Add Equation 1 and Equation 2
I+I=∫0π/2sinx+cosxsinxdx+∫0π/2sinx+cosxcosxdx
2I=∫0π/2sinx+cosxsinx+cosxdx
Step 4: Simplify and integrate
2I=∫0π/21dx
2I=[x]0π/2
2I=2π−0
I=4π
Correct Option: 4. 4π
