NDA2013MathematicsTrigonometric Ratios & IdentitiesActual
What is 15^ equal to?
Options
- A2- 3
- B2+ 3
- C1- 3
- D1+ 3
Correct answer
A. 2- 3
Step-by-step solution
From formula aligned ( A - B ) & = A - B 1+ A ~B (15^ ) & = (45^ -30^ ) & = 45^ - 30^ 1+ 45^ + 30^ & = 1- 1 3 1+1 1 3 = ( 3 -1) ( 3 +1) ( 3 -1) ( 3 -1) aligned aligned & = ( 3 -1)^2 ( 3 )^2-(1)^2 = 3+1-2 3 3-1 & = 4-2 3 2 =2- 3 aligned