Answer:
see below
Step-by-step explanation:
given: size of television is height = 37 in,  length = 71 in.
A.  using Pythagorean theorem:
parts given are legs which is the sides 
looking for the hypotenuse.
B.  formula:
a² + b² = c²    or   H² + L² = D² 
where H = height = 37
            L = length = 71
            D = diagonal (which is req'd)
C.   D² = 37² + 71² 
       D = 
       D = 
       D = 80 in (missing length)
D. size of television:
     37 x 71 in 
     Diagonal is 80 in
hope it helps and good luck!