Let the latus rectum of the hyperbola 9x2−b2y2=1 subtend an angle of 3π at the centre of the hyperbola. If b2 is equal to ml(1+n), where l and m are co-prime numbers, then l2+m2+n2 is equal to
Answer: 182
Solution
The latus rectum has half-length b2/a and subtends 60∘ at the centre, so tan30∘=aeb2/a=a2eb2=31.