Trig Identities

*=dont need to memorize, good to know and be famillar with

cos(A-B)

cosAcosB+sinAsinB

cos(A+B)

cosAcosB-sinAsinB

sin(A-B)

sinAcosB-cosAsinB

sin(A+B)

sinAcosB+cosAsinB

tan(A+B)

tanA+tanB

1-tanAtanB

tan(A-B)

tanA-tanB

1+tanAtanB

cos²A+sin²A

1

1+cot²A

csc²A

1+tan²A

sec²A

cos(2A)*

cos²A-sin²A, 1-2sin²A, 2cos²-1

sin(2A)*

2sinAcosA

tan(2A)*

2tanA

1-tan²A

cos(-x)

cos(x)

sec(-x)

sec(x)

sin(-x)

-sin(x)

csc(-x)

-csc(x)

tan(-x)

-tan(x)

cot(-x)

-cot(x)

sin(U/2)*

±sqrt(1-cosU/2)

cos(U/2)*

±sqrt(1+cosU/2)

tan(U/2)*

sinU/1+cosU