The cosine of theta is adjacent over hypotenuse, given a right triangle, theta not being the 90 degree angle, adjacent not being the hypotenuse, and theta being the angle between adjacent and hypotenuse.
In a unit triangle, i.e. in a unit circle circumscribed with radius one, and theta and the center of the circle at the origin, cosine of theta is X.
Chat with our AI personalities
Fora right angle triangle: cosine angle = adjacent/hypotenuse
In trigonometry, when we look at right triangles, the cosine is the ratio of the length of the adjacent side to the length of the hypotenuse.
phi = [(1+sqrt(5)]/2 = 1.6180, the golden ratio. cosine(phi) = -0.0472 approx.
The tangent is the ratio of sine over cosine; also, in a unit circle, Y over X.
Trig ratios or to give them their proper name are trigonometrical rations applicable to right angle triangles and they are tangent ratio, sine ratio and cosine ratio.