Trigonometry: (lesson 1 of 3)

## Trigonometric Formulas

### Reciprocal Properties:

### Quotient Properties:

### Odd/Even Identities

1. sin (-x) = -sin x

2. cos (-x) = cos x

3. tan (-x) = -tan x

4. csc (-x) = -csc x

5. sec (-x) = sec x

6. cot (-x) = -cot x

### Cofunction Identity - radians

### Cofunction Identities - degrees

### Periodicity Identities - radians

### Periodicity Identities - degrees

### Sum/Difference Identities

sin (x + y) = sin(x) cos(y) + cos(x) sin(y),

cos(x + y) = cos(x) cos(y) - sin(x) sin(y),

sin(x - y) = sin(x) cos(y) - cos(x) sin(y),

cos(x - y) = cos(x) cos(y) + sin(x) sin(y),

### Double Angle Identities

sin(2x) = 2 sin(x) cos(x),

cos(2x) = cos2(x) - sin2(x),

cos(2x) = 2 cos2(x) - 1,

cos(2x) = 1 - 2 sin2(x),

tan(2x) = [2 tan(x)]/[1-tan2(x)],

### Half Angle Identities

### Product identities

### Sum to Product Identities