Answer:
The Length of third side is 52 units.
Step-by-step explanation:
Given:
Length of First side = 48
Length of second side = 20
Also given the angle between them is 90°.
Hence we can say figure shown is a right angled triangle.
For finding the third side we can use Pythagoras theorem which states that;
"If a triangle is right angled then, the Square of the hypotenuse is equal to sum of the square of the other two sides."

Hence substituting the values we get;

Now taking Square root on both side we get;

Hence Length of Third side is 52 units.