ANSWER :
9/41
EXPLANATION :
Using Pythagorean Theorem to find the other side of the triangle :
[tex]\begin{gathered} PR^2=QP^2+QR^2 \\ 41^2=40^2+QR^2 \\ 1681=1600+QR^2 \\ QR^2=81 \\ QR=\sqrt{81} \\ QR=9 \end{gathered}[/tex]
Recall that cos angle is adjacent over hypotenuse
The adjacent side to angle R is QR and the hypotenuse is RP
That will be :
[tex]\cos R=\frac{QR}{RP}=\frac{9}{41}[/tex]
