Learn how to find the area of triangles without right angles. Find the formula to use depending on the information you know about the triangle: base and height, three sides, or two sides and an angle.

This applet allows users to study the nature of triangles and their area. It draws random triangles on a Cartesian coordinate system. The user can determine the area of the triangle using his or her preferred method. After the calculated...

To find the area of a triangle, try to make a parallelogram using a copy of the triangle.

Students explore the nature of triangles and their area. An applet and instructor resources are included. [Requires Java.]

This lesson presents the idea that the area of any right triangle is exactly half of a certain rectangle, and contains varied exercises for students.

Eighth graders are presented with a drawing of a large square inscribed by a circle which is itself inscribed by a second square. They are asked to find the area of the circle outside the smaller square and compare it to the area of the...

Explore and learn about the features and properties of a right triangle in this lesson. Includes examples and practice questions.

Learn about the perimeter of a triangle with this helpful reference tool. Provides a detailed definition, an example, and an internet activity that enhances further explanation. Includes links to related topics.

Use this calculator to calculate properties of a regular polygon. Enter any 1 variable plus the number of sides or the polygon name. Calculates side length, inradius, circumradius, area, and perimeter.