Instruction
1
If you want to find the cosine of an angle in a right triangle, you must use the definition of cosine to find the ratio of adjacent leg to the hypotenuse:
cos? = a/c where a is the length of the leg, the length of the hypotenuse.
2
If you want to find the cosine of angle in an arbitrary triangle, use the theorem of cosines:
if the angle is acute: cos? = (a2 + b2 – c2)/(2ab);
if the angle is blunt: cos? = (C2 – a2 – b2)/(2ab), where a and b are the lengths of the sides adjacent to the angle, side length opposite corner.
3
If you want to find the cosine of angle in an arbitrary geometrical figure, determine the magnitude of the angle in degrees or radians, and the cosine of the angle to find its value using scientific calculator, tables Bradis or any other mathematical application.