Use of Trigonometric functions of angles beyond 90 degrees

I learnt trigonometry recently. we can find the missing lengths or angles of a right angle triangle using the constant ratios.

But what is the utility of trigonometry ratios for angles beyond 90deg??

When do we come across the need of considering such functions with angles more 90deg ?

thanks in advance

2 Answers

Trigonometric functions are very commonly used to describe the motion of a rotating object. But once the amount of rotation passes 90 degrees, ...

• could you please complete your answer? – KawaiKx Jan 13 '14 at 23:32
• The amount of rotation can be any real number, certainly not limited to between $0$ and $90$ degrees. – Robert Israel Jan 14 '14 at 2:56

obtuse angles come up all the time. Perhaps the best example is the longitude that has to go between $-180$ and $180$.

Another example: If you look at the elevation of objects in front of you, their angle will be less than 90 degrees. Point directly above will be at 90 degrees. Points behind you will have elevation more than 90 degrees (I am only considering objects at or above the eye level).