SOLUTION: Evaluate without calculator. Variables are positive numbers. I've been trying but can't figure out what arcsin and arctan are. Thanks! cos ( arcsin 4/5 - arctan 2)
![trigonometry - Easiest way in general to find the sin, cos, arcsin, arccos, of "not so easy" angles/values without using a calculator? - Mathematics Stack Exchange trigonometry - Easiest way in general to find the sin, cos, arcsin, arccos, of "not so easy" angles/values without using a calculator? - Mathematics Stack Exchange](https://i.stack.imgur.com/cgcDO.gif)
trigonometry - Easiest way in general to find the sin, cos, arcsin, arccos, of "not so easy" angles/values without using a calculator? - Mathematics Stack Exchange
![trigonometry - Inverse trigonometric functions without calculator, arcsin, arctan - Mathematics Stack Exchange trigonometry - Inverse trigonometric functions without calculator, arcsin, arctan - Mathematics Stack Exchange](https://i.stack.imgur.com/n33pi.png)