- #1
shirozack
- 15
- 3
- TL;DR Summary
- Why does the trigo of obtuse angles use ref angles?
I would like to know the "why" of trigo of non acute angles in a unit triangle. why is it equals to the reference angle? how did it even come about?
For example, sin 150 degrees. why is it equal to sin 30?
i understand sin 30 because there is a right angle triangle of opposite and hypoteneuse etc.
but how did we resolve sin 150? how did answer became calculating the reference angle to the x-axis? why not calculate it based on the y-axis? if sin is defined as the ratio of the opposite to the hypo, then where is the opposite and hypo of a 150 angle? why is sin150 = sin30?
thanks
For example, sin 150 degrees. why is it equal to sin 30?
i understand sin 30 because there is a right angle triangle of opposite and hypoteneuse etc.
but how did we resolve sin 150? how did answer became calculating the reference angle to the x-axis? why not calculate it based on the y-axis? if sin is defined as the ratio of the opposite to the hypo, then where is the opposite and hypo of a 150 angle? why is sin150 = sin30?
thanks