The vertices B and C of a triangle ABC lie on the line x1 = 1 - y-2 = z - 23. The coordinates of A and B are (1, 6, 3) and (4, 9, α) respectively and C is at a distance of 10 units from B. The area (in sq. units) of ABC is :
- 20 13
- 5 13
- 15 13
- 10 13
Answer
(2) 5 13
Solution
Line: x1 = y - 12 = z - 23 passes through P(0, 1, 2), direction d = i + 2 j + 3 k
(B = (4, 9, α) on it gives α = 14; only BC = 10 is needed.)
Height of △ABC = distance of A(1, 6, 3) from the line:
PA = i + 5 j + k
PA d = 13 i - 2 j - 3 k, | PA d | = 182
h = 182 14 = 13
area = 12 BC h = 12 10 13 = 5 13
Answer: (2)