Trig Double-Angle Identities
For angle θ, the following double-angle formulas apply:
(2) cos 2θ = 2 cos2θ − 1
(3) cos 2θ = 1 − 2 sin2θ
(4) cos2θ = ½(1 + cos 2θ)
(5) sin2θ = ½(1 − cos 2θ)
Other Trigonometric Identities:
- Introduction to Trig Functions
- Domain, Range, and Period of Trig Functions
- Graphs of Trigonometric Functions
- Radians & Degrees
- Trig Even-Odd Identities
- Trig Reciprocal Identities
- Trig Cofunction Identities
- Trig Double-Angle Identities
- Trig Half-Angle Identities
- Trig Pythagorean Identities
- Trig Sum to Product Identities
- Trig Product to Sum Identities
- Trig Sum & Difference Identities
- Oblique Triangles: Law of Cosines
- Oblique Triangles: Law of Sines
- Polar Coordinate System
- Polar Equations & Graphs
- De Moivre's Theorem
