Math

Trigonometry Identities

• cos(a) = ADJ/HYP
• sin(a) = OPP/HYP

• sin(a+b)=sin(a)cos(b)+sin(b)cos(a)
• sin(a-c)=sin(a)cos(c)-sin(c)cos(a)
• cos(a+b)=cos(a)cos(b)-sin(a)sin(b)
• cos(a-b)=cos(a)cos(b)+sin(a)sin(b)
• $$cos(2a)=cos^2(a)-sin^2(a)$$
• $$2*cos^2(a)-1=cos(2a)$$
• $$cos^2(a)=(1/2) * (1+cos(2a))$$
• $$cos^2(a)+sin^2(a)=1$$
• $$cos(2a)=1-2sin^2(a)$$
• $$sin^2(a)=(1/2)*(1-cos(2a))$$
• $$sin(2a)=2sin(a)cos(a)$$