JAMIA 2021 — Mathematics PYQ
JAMIA | Mathematics | 2021∫cosx−cosθcos2x−cos2θdx equal to
Choose the correct answer:
- A.
2(sinx+xcosθ)+C
(Correct Answer) - B.
2(sinx−xcosθ)+C
- C.
2(xinx+2xcosθ)+C
2(sinx+xcosθ)+C
Explanation
1. Using the identity cos2A=2cos2A−1:
∫cosx−cosθ(2cos2x−1)−(2cos2θ−1)dx
2. Simplify the numerator:
∫cosx−cosθ2cos2x−1−2cos2θ+1dx
∫cosx−cosθ2cos2x−2cos2θdx
3. Factor out 2 and use a2−b2=(a−b)(a+b):
2∫cosx−cosθcos2x−cos2θdx
2∫cosx−cosθ(cosx−cosθ)(cosx+cosθ)dx
4. Cancel the common term (cosx−cosθ):
2∫(cosx+cosθ)dx
5. Integrate with respect to x (Note: cosθ is a constant):
2[∫cosxdx+∫cosθdx]
2[sinx+xcosθ]+C
Final Answer:
2(sinx+xcosθ)+C
Explanation
1. Using the identity cos2A=2cos2A−1:
∫cosx−cosθ(2cos2x−1)−(2cos2θ−1)dx
2. Simplify the numerator:
∫cosx−cosθ2cos2x−1−2cos2θ+1dx
∫cosx−cosθ2cos2x−2cos2θdx
3. Factor out 2 and use a2−b2=(a−b)(a+b):
2∫cosx−cosθcos2x−cos2θdx
2∫cosx−cosθ(cosx−cosθ)(cosx+cosθ)dx
4. Cancel the common term (cosx−cosθ):
2∫(cosx+cosθ)dx
5. Integrate with respect to x (Note: cosθ is a constant):
2[∫cosxdx+∫cosθdx]
2[sinx+xcosθ]+C
Final Answer:
2(sinx+xcosθ)+C

