## Quick Reference

Functions defined in terms of a right-angled triangle (see diagram) and widely used in the solution of many mathematical problems. They are defined as: tangent of angle *A*, written tan*A* = *a*/*b* sine of angle *A*, written sin*A* = *a*/*c* cosine of angle *A*, written cos*A* = *b*/*c*,

tangent of angle *A*, written tan*A* = *a*/*b*

sine of angle *A*, written sin*A* = *a*/*c*

cosine of angle *A*, written cos*A* = *b*/*c*,

where *a* is the length of the side opposite the angle *A*, *b* is the length of the side opposite the angle *B*, and *c* is the hypotenuse of the triangle. The reciprocal functions are: cotangent of angle *A*, written cot*A* = 1/tan*A* = *b*/*a* secant of angle *A*, written sec*A* = 1/cos*A* = *c*/*b* cosecant of angle *A*, written cosec*A* = 1/sin*A* = *c*/*a*

cotangent of angle *A*, written cot*A* = 1/tan*A* = *b*/*a*

secant of angle *A*, written sec*A* = 1/cos*A* = *c*/*b*

cosecant of angle *A*, written cosec*A* = 1/sin*A* = *c*/*a*

**Trigonometric functions.**

*Subjects:*
Mathematics.

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