Draw a rectangle that is 15cm long and 8cm wide. Draw a diagonal in it and find the area of a right-angled triangle.

From the construction and condition of the problem, we know two legs of a right-angled triangle, and we also know the length and height of the rectangle;

There are two ways to find the area of the resulting right-angled triangle;

1. Find the area of a rectangle and divide it by two;

2. Substitute the available data into the formula for the area of a right-angled triangle;

The first way;

Find the area of the rectangle;

S = 15 * 8 = 120cm2;

Str = 120/2 = 60cm2;

Second way;

Formula for the area of a right-angled triangle;

Str = a * b / 2 = 15 * 5/2 = 60cm2.