Cosine Calculator

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

# Graph of cosine

Graphical demonstration of cos function

# Cosine table

Degrees
Radians
cos
0
0
1
30
π / 6
√ 3 / 2
45
π / 4
1 / √ 2
60
π / 3
1 / 2
90
π / 2
0
180
π
-1
270
3π / 2
0
360
2π
1