Demonstration (Classification by Lengths of Sides and Classification by Angle Measure)

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Instructions text as in global.js

Perimeter of a Triangle

Area of the Interior of a Triangle

b: The length of a base (side) of a triangle

a: The length of the altitude of the triangle (corresponding to the chosen base)

A: The area of the interior of the triangle (Explanation of formula).

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Click here to see an applet that demonstrates the area formula.

Other Components of Triangles

- Altitude(s) of a triangle: a segment from a vertex of the triangle, perpendicular to the side opposite that vertex of the triangle.
- Angle bisector(s) of a triangle: a segment, ray or line which divides an angle of the triangle into two congruent (equal in measure) parts.
- Median(s) of a triangle: a segment from a vertex of the triangle, to the midpoint of the side opposite that vertex of the triangle.

Right Triangles

Right triangles are labelled according to a chosen reference angle. The hypotenuse (h) is labelled first, then the legs are labelled as opposite (o) or adjacent (a), depending on which remaining angle is chosen as the reference angle.

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Right triangles are often solved using the following:

- Angles in any triangle sum to 180°.
- The Pythagorean theorem.
- Trigonometric ratios.

Non-Right Triangles

Non-right triangles are often solved using the following:

- Angles in any triangle sum to 180°.
- The cosine law.
- The sine law.