NDA2014MathematicsTrigonometric Ratios & IdentitiesActual
What is 1+ A 1- A - 1- A 1+ A equal to?
Options
- AA - A
- B2 ~A ~A
- C4 ~A ~A
- D4 cosec A A
Correct answer
C. 4 ~A ~A
Step-by-step solution
aligned & 1+ A 1- A - 1- A 1+ A = & (1+ A )^2-(1- A )^2 (1- A )(1+ A ) = & (1+2 ~A + ^2 ~A )- (1-2 ~A + ^2 ~A ) 1- ^2 ~A = & 1+2 ~A + ^2 ~A -1+2 ~A - ^2 ~A ^2 ~A = & 4 ~A ~A A =4 ~A ~A . aligned