STRAIGHT LINE....... LOCUS... please help...

A & B are fixed points.
The vertex C of triangle ABC moves such that cot a + cot b=constant.
The locus of C is a straight line

a> perpndicular to AB.
b> parallel to AB.
c> inclined at angle(A-B) to B.
d> none of the above.

please post the soln. along with the answr...
please help...

2 Answers

drop a perpendicular from C on AB let the foot be D

\cot A + \cot B =\frac{1}{CD}*AB(constant)
this implies

CD =constant

which means parallel line to AB

thanx a lot.,...
got it...

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