This study sheet has ten groups of trig identities for the basic trigonometry functions. These identities include the reciprocal and co-function relationships between trig functions. There are also half-angle and double angle identities, along with sum and product relationships. This table is an extremely useful thing to keep on hand when working with trig functions. Print a copy and keep it with your textbook today.

### Trig Identities

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### Sine, Cosine, Tangent, Cotangent, Secant, Cosecant

The sine (sin), cosine (cos), tangent (tan), cotangent (cot), secant (sec), and cosecant (cos) of an angle θ are all ratios of the sides of a right triangle.

- sin θ = opposite / hypotenuse
- cos θ = adjacent / hypotenuse
- tan θ = opposite / adjacent
- cot θ = 1 / tan = adjacent / opposite
- sec θ = 1 / cos = hypotenuse / adjacent
- cos θ = 1 / sin = hypotenuse / opposite