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.
The Math/Science
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.
Triangle Calculators
- 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
References
- Light and Matter(Dr. Benjamin Crowell) Chapter 0.12 Summary