NTA Abhyas JEE Main2020MathematicsDefinite IntegrationPractice
The value of ∫ 0 π ( ∑ r = 0 3 a r cos 3 − r x sin r x ) d x depends upon
Options
- Aa 1 and a 2
- Ba 0 and a 3
- Ca 2 and a 3
- Da 1 and a 3
Correct answer
D. a 1 and a 3
Step-by-step solution
Let, I = ∫ 0 π ∑ r = 0 3 a r cos 3 - r x sin r x d x = ∫ 0 π a 0 cos 3 x d x + ∫ 0 π a 1 cos 2 x sin x d x + ∫ 0 π a 2 cos x sin 2 x d x + ∫ 0 π a 3 sin 3 x d x Since, ∫ 0 2 a f x d x = 2 ∫ 0 a f x d x , i f f 2 a - x = f ( x ) 0 , i f f 2 a - x = - f ( x ) ∴ Integral Ist and IIIrd become zero. ∴ The given integral depends upon a 1 and a 3 .