Sine and cosine are written using functional notation with the abbreviations sin and cos.
Often, if the argument is simple enough, the function value will … See more

Zero is the only real fixed point of the sine function; in other words the only intersection of the sine function and the identity function See more

Sine and cosine are used to connect the real and imaginary parts of a complex number with its polar coordinates (r, φ):
$${\displaystyle z=r(\cos(\varphi )+i\sin(\varphi ))}$$ See more

Right-angled triangle definitions
To define the sine and cosine of an acute angle α, start with a right triangle that contains an angle … See more

Exact identities (using radians):
These apply for all values of $${\displaystyle \theta }$$.
Reciprocals See more

The law of sines states that for an arbitrary triangle with sides a, b, and c and angles opposite those sides A, B and C: See more

While the early study of trigonometry can be traced to antiquity, the trigonometric functions as they are in use today were developed in the medieval period. The chord function … See more