Processing Math: Done

From Förberedande kurs i matematik 1

Because one of the angles in the triangle is 90°, we have a right-angled triangle and can use the Pythagorean theorem to set up a relation between the triangle's sides.

The side of length 13 is the hypotenuse in the triangle, and the Pythagorean theorem therefore gives us that

132=122+x2

i.e.

x2=132−122.

This means that

x=132−122=169−144=25=5.