Trig Identities Equations

Tangents

• tan(x)=sin(x)/cos(x)
• Look for tangents in equations and Sins over cosins to expand

Secants

• Sec(x)=1/cos(x)
• Look for cosins in denominator, especially near end of equations

Cosecants

• Csc(x)=i/sin(x)
• Look for sins in the denominator, especially towards the end of solving

Cotangents

• Cot(x)=cos(x)/sin(x)

Pythagorean Identities- Sin and Cosin

• Sin^2(x)+cos^2(x)=1
• Look for that equation or one of the components minus once, eg sin^2(x)-1 would equal cos^2(x)

Pythagorean Identities- Tan and Sec

• 1+tan^2(x)=sec^2(x)

Pythagorean Identities- Cot and Csc

• 1+cot^2(x)=csc^2(x)

Co-Function Identities

• Sin(pi/2-x)=cos(x)
• Tan(pi/2-x)=cot(x)
• Csc(pi/2-x)=sec(x)
• Cos(pi/2-x)=sin(x)
• Cot(pi/2-x)=tan(x)
• Sec(pi/2-x)=csc(x)