Consider a triangle ABC having the vertices A(1, 2), B( , ) and C( , ) and angles = 6 and = 2 3. If the points B and C lie on the line y = x + 4, then 2 + 2 is equal to .
Answer
14
Solution
= 6 and = - 2 3 - 6 = 6, so both AB and AC make an angle 6 with BC: y = x + 4.
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BC has slope 1 (inclined at 45 ), so these two lines are inclined at 45 30 , i.e. slopes 75 = 2 + 3 and 15 = 2 - 3.
AB, AC: y - 2 = (2 3)(x - 1); meeting y = x + 4 gives x + 2 = (2 3)(x - 1)
Slope 2 + 3: (1 + 3)x = 4 + 3 x = 3 3 - 12
Slope 2 - 3: (1 - 3)x = 4 - 3 x = - 3 3 + 12
These x-values are and , hence 2 + 2 = (3 3 - 1)2 + (3 3 + 1)24 = 2(27 + 1)4 = 14
Answer: 14