# Triangle

 Definition: A triangle is a polygon with 3 sides. Types of triangles by sides   Definitions   Directions for interactivity Scalene triangle has three different sides. Isoceles triangle has two equal sides. Equilateral triangle has three equal sides. ("equal" or "congruent" sides, that is, having equal length) Directions: In the interactivity, click and drag the sliders for side length and notice what kind of triangle is generated. equal sides means equal angles! Click and drag slider zoom to zoom in or out (and get similar triangles!). Click and drag point А to move and point В to rotate. This browser does not have a Java Plug-in. Get the latest Java Plug-in here.
 Rule: The sum of the inside angles of a triangle is 180°. Types of triangles by angles   Definitions   Directions for interactivity Acute triangle is a triangle with all three inside angles <90°. Right triangle is a triangle with one inside angle =90°. Obtuse triangle is a triangle with one inside angle >90°. Directions: In the interactivity, click and drag the angle sliders \alpha and \beta and notice the third angle \gamma is automatically fixed by the formula \alpha + \beta + \gamma = 180^\circ the change in the type of triangle that is created. Click and drag slider zoom to zoom in or out (and get similar triangles!). Click and drag point А to move and point В to rotate. This browser does not have a Java Plug-in. Get the latest Java Plug-in here.
 Formulas for perimeter and area

Related themes: