Question

Trigonometric angles without a calculator

Answer 1

`~~~~~~~\cos x = \frac{ \text{Base}}{\text{Hypotenuse}}\\ \\\\\implies \cos x= (9)/(18)\\\\\\\implies \cos x = \frac 12\\\\\\\implies x= \cos^(-1) \left( \frac 12\right)\\ \\ \\\implies x = 60^(\circ)`