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I have two questions regarding the trigonometric functions (sinx,cosx,tanx etc).

1) What is the geometric meaning (i.e in the context of a right-angle triangle) of functions like cos(180°) or any of the trigonometric functions with an obtuse angle? I mean a right-angle triangle can not contain an obtuse angle so I don't understand how we can have ratios of two sides of a right-triangle that isn't even a right-triangle to begin with (if that makes any sense)?

2) Why are these functions negative for some angles? Since these are just ratios of any two lengths of a right-triangle and lengths usually aren't negative.

Pardon my ignorance and thank you for your precious time! :)