[tex]\begin{gathered} To\text{ solve the question, then i have  to use the trig function.} \\ \text{Hy}potenuse\text{ = 21 ,  Adjacent = 15} \\ Using\text{ Cos x  = }\frac{Adj}{\text{Hyp}} \\ \text{          cos x = }\frac{15}{21} \\ \text{         cos x = 0.714} \\ \text{ x = cos}^{-1}(0.714) \\ \text{ x = 44.42} \end{gathered}[/tex]