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