We encounter similar difficulties when we substitute rectangles for triangles in this configuration.

Some important geometric shapes are the triangle, the square, the rectangle, the circle, the parallelogram and the trapezium.

The opposite sides of a rectangle are parallel.

A rectangle has four right angles.

The area of a triangle is half of the area of the rectangle with equivalent base and height.

Important geometric figures, that are triangle, square, rectangle, circle, parallelogram and trapeze.

All squares are rectangles.

A square is always a rectangle, but a rectangle is not always a square.

Every square is a rectangle.

The Japanese flag is a white rectangle with a red circle in the centre representing the sun.