Take an x-axis and an y-axis (orthonormal) and let O be the origin. A circle centered in O and with radius = 1 is known as trigonometric circle or unit circle.
If P is a point from the circle and A is the angle between PO and x axis then:
- the x-coordinate of P is called the cosine of A. We write cos(A) or cos A;
- the y-coordinate of P is called the sine of A. We write sin(A) or sin A;
- the number sin(A)/cos(A) is called the tangent of A. We write tan(A) or tan A;
- the number cos(A)/sin(A) is called the cotangent of A. We write cot(A) or cot A.
The sine function
sin : R -> R
All trigonometric functions are periodic. The period of sin is 2.
The range of the function is [-1,1].
All trigonometric functions are periodic. The period of sin is 2.
The range of the function is [-1,1].
The cosine function
cos : R -> R
The period of sin is 2.
The range of the function is [-1,1].
The period of sin is 2.
The range of the function is [-1,1].
The tangent function
tan : R -> R
The range of the function is R. Now, the period is and the function is undefined at x = (/2) + k, k=0,1,2,...
The graph of the tangent function on the interval 0 -
The range of the function is R. Now, the period is and the function is undefined at x = (/2) + k, k=0,1,2,...
The graph of the tangent function on the interval 0 -
Animated graph(open in a new window):
The graph of the tangent function on the interval 0 - 2
The graph of the tangent function on the interval 0 - 2
The cotangent function
cot : R -> R
The range of the function is R. The period is and that the function is undefined at x = k, k=0,1,2,...
The range of the function is R. The period is and that the function is undefined at x = k, k=0,1,2,...
The values of sin, cos, tan, cot at the angles of 0°, 30°, 60°, 90°, 120°, 135°, 150°, 180°, 210°, 225°, 240°, 270°, 300°, 315°, 330°, 360°
The easiest way to remember the basic values of sin and cos at the angles of 0°, 30°, 60°, 90°:
sin([0, 30, 45, 60, 90]) = cos([90, 60, 45, 30, 0]) = sqrt([0, 1, 2, 3, 4]/4)
sin([0, 30, 45, 60, 90]) = cos([90, 60, 45, 30, 0]) = sqrt([0, 1, 2, 3, 4]/4)
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