Definition: In geometry, a triangle is a 2dimensional figure with three sides. Definition: A righttriangle is a triangle with a right angle (90° angle) Interactivity 1: Right triangle Directions for interactivity Click and drag blue points in construction to move and rotate. Click and drag blue endpoints of base and height line to resize triangle. 
Basic formulas for triangles.
Examples with perimeter and area of righttriangles

Interactivity 2: Construct a righttriangle with the given base and height.
This is a compass and straightedge (compass and ruler) construction.
First, you will need to construct 2 perpendicular lines  Mathcast
Then, using your compass tool, mark out the radius of the base on one perpendicular and the radius of the height on the other.
Get the latest Java Plugin here. 
Equivalent Definitions:
Theorems

Related themes:
 Triangle, Similar, Congruent
 Medians of Triangles,
 Paralelogram, Rectangle
 Rhombus, Trapezoid, Quadrilateral
 Polygons, Triangles, Kite (Deltoid)
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