Search results
Results from the WOW.Com Content Network
The six trigonometric functions are defined for every real number, except, for some of them, for angles that differ from 0 by a multiple of the right angle (90°). Referring to the diagram at the right, the six trigonometric functions of θ are, for angles smaller than the right angle:
When the direction of a Euclidean vector is represented by an angle , this is the angle determined by the free vector (starting at the origin) and the positive -unit vector. The same concept may also be applied to lines in a Euclidean space, where the angle is that determined by a parallel to the given line through the origin and the positive x ...
In the last step we took the reciprocals of the three positive terms, reversing the inequities. Squeeze: The curves y = 1 and y = cos θ shown in red, the curve y = sin( θ )/ θ shown in blue. We conclude that for 0 < θ < 1 / 2 π, the quantity sin( θ )/ θ is always less than 1 and always greater than cos(θ).
Similar right triangles illustrating the tangent and secant trigonometric functions Trigonometric functions and their reciprocals on the unit circle. The Pythagorean theorem applied to the blue triangle shows the identity 1 + cot 2 θ = csc 2 θ, and applied to the red triangle shows that 1 + tan 2 θ = sec 2 θ.
In this right triangle, denoting the measure of angle BAC as A: sin A = a / c ; cos A = b / c ; tan A = a / b . Plot of the six trigonometric functions, the unit circle, and a line for the angle θ = 0.7 radians. The points labeled 1, Sec(θ), Csc(θ) represent the length of the line segment from the origin to that point.
The tangent half-angle substitution relates an angle to the slope of a line. Introducing a new variable = , sines and cosines can be expressed as rational functions of , and can be expressed as the product of and a rational function of , as follows: = +, = +, = +.
The converse is not true: there are entire transcendental functions f such that f (α) is an algebraic number for any algebraic α. [6] For a given transcendental function the set of algebraic numbers giving algebraic results is called the exceptional set of that function. [7] [8] Formally it is defined by:
A number x 0 is said to be a fixed point of a function f(x) if f(x 0) = x 0; in other words, if f leaves x 0 fixed. The fixed points of a function can be easily found graphically: they are simply the x coordinates of the points where the graph of f(x) intersects the graph of the line y = x.