Theta Symbol
The Greek letter theta is used in mathematics as a variable usually associated with a measured angle. For example, the symbol theta appears in the three main trigonometric functions: sine, cosine, and tangent as the input variable.
In plain language, this represents the cosine function which takes in one argument represented by the variable .
Symbol  Format  Data 

θ  Unicode 

TeX 


SVG 
Usage
An angle is defined as the amount of rotation between two rays. Angles are measured using degrees and radians. A full rotation in degrees is 360°. A full rotation in radians is approximately 6.283 radians or τ (tau) radians.
The cosine function returns the cosine of an angle provided in radians. In geometric terms, the function returns the ratio of the righttriangle's adjacent side over its hypotenuse.
The sine function returns the sine of a number provided in radians. In geometric terms, given the angle of a righttriangle as input, the function returns the ratio of the triangle's opposite side over its hypotenuse.
Given the angle of a right triangle as input returns the ratio of the triangle's opposite side over its adjacent side.
Related Symbols
The capital Greek letter (Θ).