We will solve this by using the law of cosines as follows:
[tex]c^2=a^2+b^2-2ab\cos (C)[/tex]
And we replace as follows (We have that the angles is 90 degrees from the triangles):
[tex]z^2=40^2+9^2-2(40)(9)\cos (90)\Rightarrow z=\sqrt[]{40^2+9^2-2(40)(9)\cos(90)}\Rightarrow z=41[/tex]
So, the value of z is 41.
