Let 0< <1, = 13 and -1(1- )+ -1(1- )= 4. Then 6( + ) is equal to :
- 6
- 7
- 8
- 9
Answer
(2) 7
Solution
Taking tangent of both sides :
(1- )+(1- )1-(1- )(1- )= 4=1
2- - =1-(1- - + )= + -
2( + )=2+
= 13 = 13
2( + )= 73 6( + )=7
Check : + = 76, = 13 give \ , \= \ 23, 12 \; 1- and 1- are positive with product less than 1, so the two angles really add up to 4
Answer: (2)