Trig identities 1/30

sin2x

2sinxcosx

cos2x : 1

cos²x-sin²x

cos2x : 2

1-2cos²x

cos2x : 3

2sin²x - 1

tan2x

2tanx / 1 - tan²x

sin²x

1-cos2x/2

cos²x

1+cosx/2

tan²x

1-cosx/1+cosx

sin (x/2)

+-sqrt (1-cosx/2)

cos (x/2)

+-sqrt (1+cosx/2)

tan (x/2)

+- sqrt (1-cosx/1+cosx)

tan (x/2) : 2

1-cosx/sinx

tan (x/2) : 3

sinx/1+cosx

sinasinb

½ [cos (a - b) - cos (a+b)]

cosacosb

½[cos (a - b) + cos (a + b)]

sinacosb

½[sin (a+b) + sin (a-b)]

cosasinb

½[sin (a+b ) - sin (a-b)]

sina + sinb

2sin(a+b/2)cos(a-b/2)

sina - sinb

2cos(a+b/2)sin(a-b/2)

cosa + cosb

2cos(a+b/2)cos(a-b/2)

cosa - cosb

-2sin(a+b/2)sin (a-b/2)