In an obtuse isosceles triangle, one of the sides is 9cm larger than the other and the perimeter is 45cm. Find the sides.

By condition, an isosceles triangle is obtuse, which means that the base of the triangle is greater than the other two equal sides.

Imagine the size of one of the equal sides in the form of an unknown, that is, X. Then the length of the base will be X + 9, since by condition it is larger.

The perimeter of the triangle is defined as the sum of the three sides, that is, X + X + (X + 9). Or 45 – according to the condition of the problem. Thus, we get an equation, which we solve for X:

X + X + (X + 9) = 45;

3 * X = 45 – 9;

X = 36/3;

X = 12.

So, one of the equal sides is 12, then the base of the triangle is 12 + 9 = 21.

Answer: the sides of the triangle are 12, 12, 21.