Not exactly true. If you know only three angles, there exist an infinite number of possible side lengths.

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- December 31st 2011, 10:33 AMHallsofIvyRe: A Question of Definitions of Trig Functions
- December 31st 2011, 12:07 PMcorsicaRe: A Question of Definitions of Trig Functions
You're right. Sorry, my bad. I should had said: three parameters always fix the shape of a triangle, but not necessarily its scale size.

Full overview to clear up any confusion:

- 3 side lengths known -> all angles can be calculated
- 3 angles known -> all side-ratios can be calculated, but not the absolute side lengths
- 1 angle and 2 side lengths known -> all other side lengths and angles can be calculated
- 2 angles and 1 side length known -> all other side lengths and angles can be calculated