Let A(1, 0), B(2, -1) and C ( 73, 43 ) be three points. If the equation of the bisector of the angle ABC is x + y = 5, then the value of 2 + 2 is
- 5
- 10
- 8
- 13
Answer
(2) 10
Solution
The bisector of angle ABC passes through B along the sum of the unit vectors along BA and BC.
BA = (-1, 1), | BA| = 2
BC = ( 13, 73 ), | BC| = 503 = 5 23
Unit vectors: 1 2(-1, 1) and 15 2(1, 7)
direction of bisector 15 2 [(-5, 5) + (1, 7) ] (-4, 12) (-1, 3)
slope = -3; line through B(2, -1): y + 1 = -3(x - 2)
3x + y = 5
= 3, = 1 2 + 2 = 9 + 1 = 10
Answer: (2)