Question

ABC is a triangle A = (2, 3, 5), B = (–1, 3, 2) and

C = (l, 5, m). If the median through A is equally inclined to the axes, then –

• A. l = m = 5
• B. l = 5, m = 7
• C. l = 7, m = 10
• D. l = 0, m = 0

Answer 1

Answer: (C)

l = 7, m = 10

Answer 2

Mid point of BC is

$\left( \frac{\lambda - 1}{2},4,\frac{2 + \mu}{2} \right)$

DR's of median through A

are -

$\frac{\lambda - 1}{2}$ – 2, 4 – 3, $\frac{2 + \mu}{2}$ – 5

i.e. $\frac{\lambda - 5}{2}$, 1, $\frac{\mu + 8}{2}$

The medium is equally inclined to axes,

\ D.R's must be

equal $\frac{\lambda - 5}{2}$ = 1 = $\frac{\mu + 8}{2}$

Ž l = 7 and µ = 10