Let ABC be an isosceles triangle in which A is at (-1,0), A= 2 3,AB=AC and B is on the positive x-axis. If BC=4 3 and the line BC intersects the line y=x+3 at ( , ), then 4 2 is .
Answer
36
Solution
= =30 ; sine rule: AB 30 = 4 3 120 =4
[figure]
(3,0); AC makes 120 with x-axis (-1-2, 2 3)=(-3,2 3)
BC: slope =- 1 3 x+ 3y=3
With y=x+3: (1+ 3)y=6 = 61+ 3, = -3= 3 (1- 3 )1+ 3
4 2= 649 (1- 3 )2 (1+ 3 )2= 144(1-3)2=36
(C below the x-axis gives the same value.)
Answer: 36