What does it mean to refer to a 20-in TV set or a 25-inch TV set? Such units refer to the diagonal of the screen. A 20-in. TV set also has a width of 16 inches. What is its height?
Use the Pythagorean theorum for a right triangle:
a^2 + b^2 = c^2, where c is the hypotenuse and a and b are the other two sides.
Insert your values for a and c and solve for b.
I hope this helps. Thanks for asking.