Oblique Triangle
Calculate oblique triangles.
An oblique triangle is any triangle that is not a right angled triangle.
Triangle Three Known Values  Length and Angle Calculator
Calculate the unknown lengths and angles in a triangle. Add three known values  leave the rest of the inputs blank.
Note!  the calculator is based on the same value combinations used in the equations below. Other value combinations will not work  most triangles with three known values can be adapted to these equations. The calculator is quite simple. With strange results  check your input values.
Angle A (degrees)
Angle B (degrees)
Angle C (degrees)
Length a (m, mm, ft, in ..)
Length b (m, mm, ft, in ..)
Length c (m, mm, ft, in ..)
Area (m^{2}, mm^{2}, ft^{2}, in^{2} .....):
(enable popup)
A, B and a is known, calculate
b = a sin(B) / sin(A) (1a)
C = 180^{o}  (A + B) (1b)
c = a sin(C) / sin(A) (1c)
A, a and b is known, calculate
sin(B) = b sin(A) / a (2a)
C = 180^{o}  (A + B) (2b)
c = a sin(C) / sin(A) (2c)
a, b and C is known, calculate
tan(A) = a sin(C) / (b  a cos(C)) (3a)
B= 180^{o}  (A + C) (3b)
c = a sin(C) / sin(A) (3c)
a, b and c is known, calculate
cos(A) = (b^{2} + c^{2}  a^{2}) / (2 b c) (4a)
cos(B)= (a^{2} + c^{2}  b^{2}) / (2 a c) (4b)
C = 180^{o}  (A + B) (4c)
a, b, c, A, B and C is known, calculate area
s = (a + b + c) / 2 (5a)
area = (s (s  a) (s b) (s  c))^{1/2} (5b)
area = b c sin(A) / 2 (5c)
area = a^{2} sin(B) sin(C) / (2 sin(A)) (5d)
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