

InterviewSolution
Saved Bookmarks
1. |
`int("sin"(5x)/(2))/("sin"(x)/(2))dx` is equal to (where, C is a constant of integration)A. `2x + "sin" x + 2 "sin" 2x + C`B. `x + 2"sin" x + 2 "sin" 2x + C`C. `x + 2"sin" x + "sin" 2x + C`D. `2x + "sin" x + "sin" 2x + C` |
Answer» Correct Answer - C Let `I=int("sin"(5x)/(2))/("sin"(x)/(2))dx = int("2 sin"(5x)/(2)"cos"(x)/(2))/("2 sin"(x)/(2)"cos"(x)/(2))dx` [multiplying by `"2 cos"(x)/(2)` in numerator and denominator] `=int(sin3x + sin2x)/(sin x)dx` `[therefore 2 sin A cos B = sin(A+B)+sin(A-B)and sin 2 A = 2 sin A cos A]` `= int((3 sin x - 4 sin^(3) x)+2 sin x cos x)/(sin x)dx" "[therefore sin 3x = 3 sin x -4 sin^(3) x]` `= int(3-4 sin^(2)x + 2 cos x)dx` `=int[3-2(1-cos 2x)+2 cos x]dx" "[therefore 2 sin^(2)x=1 - cos 2x]` `= int[3-2+2 cos 2x + 2 cos x]dx` `=[1+2 cos 2x + 2 cos x]dx` `=x+2 sin x + sin 2x + C` |
|