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`"AA" = 2 * tan^-1( sqrt(((s- "b" )(s- "c" ))/(s*(s- "a" )))) _(where) "s" = ( "a" + "b" + "c" )/2`

Enter a value for all fields

The **Triangle Angle** calculator computes the interior angle (AA) of a triangle given the length of the three sides (a, b & c).

**INSTRUCTIONS:** Choose units and enter the following:

- (
**a**) the length of side a - (
**b**) the length of side b - (
**c**) the length of side c

**Triangle Angle (AA):** The calculator returns the angle in degrees. However, this can be automatically converted to other angle units (e.g. radians) via the pull-down menu.

This is derived from the following equation:

`tan("AA"/2) = sqrt( ((s-b)(s-c)) / (s*(s-a)) )` where the semi-perimeter: `s = (a + b + c)/2`

A **triangle** is a polygon with three sides, three vertices (corners), and three angles. **Triangles **can be classified based on the lengths of their sides and the measures of their angles as follows:

By Side Lengths:

**Equilateral Triangle**: All three sides are equal in length.**Isosceles Triangle**: Two sides are equal in length.**Scalene Triangle**: All three sides have different lengths.

By Angle Measures:

**Acute Triangle**: All three angles are less than 90 degrees.**Right Triangle**: One angle is exactly 90 degrees.**Obtuse Triangle**: One angle is greater than 90 degrees.

The sum of the interior angles of any triangle always adds up to 180 degrees.

- Area of Triangle (base and height)
- Area of Triangle (two sides and interior angle)
- Area of Triangle (two angles and interior side)
- Area of Triangle (three sides)
- Area of Equilateral Triangle
- Area of Triangle (three points)
- Height of Triangle
- Width of Triangle
- Triangle Perimeter
- Interior Angle of a triangle based on the length of three sides
- Semi-perimeter of a triangle
- Area of Circle Within a Triangle
- Area of Circle Around a Triangle
- Area between two vectors
- Triangle Volume

- Light and Matter(Dr. Benjamin Crowell) Chapter 0.12 Summary