For , , 0, if -1 + -1 + -1 = and ( + + )( - + )=3 , then equals
- 3
- 32
- 1 2
- 3-12 2
Answer
(2) 32
Solution
Let -1 =A, -1 =B, -1 =C ⇒ A+B+C=
∵ each angle lies in [- 2, 2 ] and is non-zero, all three are positive ⇒ A, B, C are the angles of a triangle whose sides are ∝ A, B, C, i.e. ∝ , , (sine rule)
Given: ( + )2- 2=3 2+ 2- 2=
C= 2+ 2- 22 = 12 (cosine rule)
C= 3 = 3= 32
Answer: (2)