Trigonometric cosine calculator
# What is Cosine?
Cosine is considered to be one of the oldest mathematical functions. The word cosine consists of two parts "co" and "sine" which indicates that cosine is the sine of the complementary angle.
Cosine is commonly referred to as "cos". Cosine of a right-angled triangle is defined as "the ratio of the length of the adjacent side to the length of hypotenuse"
# Law of cosine formulas
Cosine rule can be used for any triangle (whether it is right-angled triangle or not) to relate all the side of the triangle to one angle.
Rule for finding sides:
a2 = b2 + c2 - 2bc * cos(A)
- b2 = a2 + c2 - 2ac * cos(B)
- c2 = a2 + b2 - 2ab * cos(C)
Rule for finding angles:
cos(A) = b2 + c2 - a2 / 2bc