Question

Someone please help me

Answer 1

Pythagorean theorem is $a^{2} + b^{2} = c^{2}$
and using that sin is opposite/hypotenuse, you can find the third side of the triangle.
$11^{2}+(adjacent)^{2} = 61^{2} \\ 121+ (adjacent)^{2} = 3721 \\ (adjacent)^{2}=3600 \\ adjacent = 60$
now you know adjacent is 60, so cos=60/61