We're assuming the TV is a rectangle, meaning all corners have right angles.
From the given information, we have a right triangle with a height of 39 inches, hypotenuse, of 80 inches, and an unknown base width.
Using Pythagorean's theorem:
[tex]a^2+b^2=c^2[/tex]
[tex]b=\sqrt{c^2-a^2}[/tex]
c = 80 and a = 39
[tex]b=\sqrt{80^2-39^2}[/tex]
[tex]=\sqrt{4879}[/tex]
Using a calculator and rounding to the nearest tenth gives
[tex]\approx 69.8 \text{ inches}[/tex]
Let me know if you need any clarifications, thanks!
