What is the height of the following triangle if the area is 60 m²

Can you me find the missing length. i attached an image.

If cos(2x) = tan^2(y), show that cos(2y) = tan^2(x).

Find the volume of the solid obtained by rotating the region enclosed by the curves y=1x and y=7^-x about the x-axis. (use symbolic notation and fractions where needed.) volume =