That is a brilliant way to do it. Short and no complicated trig stuff. I am in awe. ( no dazzled-smiley-face available)

Bob

]]>My solution extends the line AB and names E the foot of the perpendicular from C to that line. Then I used The basic trig equations to get the result.

]]>What does 'quite a bit of inspection' mean exactly.

Bob

]]>Here's an outline of a way to prove this. see diagram below.

There's no right angle to get tanA easily so I used the sine and cosine rules:

and

Put these together to get tanA and simplify.

work on this expression for tanA, making use of the following:

After much simplification you can get this equal to -2tanB, from which the required result follows.

It's a tough one so expect it to take 2 or 3 pages. If you get stuck post back where you've got to, and I'll compare your answer with mine.

Bob

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