Hi Forum

Here is a question

I am confused about the usage of cotg in this formula. How was this formula calculated?

If we use only tg we'd get

This angle regards the angle of the side , correct?

I'm no pro in co-trigonometric functions but,

Will this, in any way, relate to the fundamental propriety of cotg=A/O?

Trigonometric functions on non right angles are rather strange.

Thanks.