Trigonometric Double Angle Formulas

Double Angle Formulas

• $$\sin \left(2x\right)=2\sin \left(x\right)\cos \left(x\right)$$
• $$\cos \left(2x\right)={\cos \left(x\right)}^2-{\sin \left(x\right)}^2=2{\cos \left(x\right)}^2-1=1-2{\sin \left(x\right)}^2$$
• $$\tan \left(2x\right)=\frac{2\tan \left(x\right)}{1-{\tan \left(x\right)}^2}$$