BITSAT2012MathematicsTrigonometric Ratios & IdentitiesActual
If ² + ² =1 / 2, ² + ² =3 / 2, then ²( - ) is equal to
Options
- A3 / 8
- B5 / 8
- C3 / 4
- D5 / 4
Correct answer
B. 5 / 8
Step-by-step solution
Using cosine formula 2 ( + ) ( - )=1 / 2 ...(i) 2 ( + ) ( - )=3 / 2 ...(ii) Squaring (1) and (2) and then adding ²( - )= 1 4 + 9 4 = 5 2 ²( - )= 5 8