trigonometry formulas

*Length of arc =radius×angle subtends at center
*Conversation between degree  and radian measure
Degree measure = (180°÷π)×radian measure
Radian measure =(π÷180°)×degree measure
Trigonometry ratio
Sin²x + Cos²x=1
Sec²x - tan²x=1
Cosec²x - Cot²x =1
* Signs of trigonometric in quadrant
All trigonometry are positive in 1st quadrant(0° to 90° or 0 to π/2)
All trigonometry are negative except sinx and cosecx in 2nd quadrant (90° to 180° or π/2 to π )
All trigonometry are negative except tan and cotx in 3rd quadrant (180° to 270° or π  to 3π/2)
All trigonometry are negative except cosx and secx (270° to 360° or 3π/2 to 2π)
Sin(-x)= -Sinx
Cos(-x) = Coax
Sec(-x) = Secx
Cosec(-x) = -Cosecx
tan(-x) = -tanx
Cot(-x) = Cotx

Sin(x+y) = SinxCosy +CosxSiny
Sin(x-y) = SinxCosy - CosxSiny
Cos(x+y) = CosxCosy - SinxSiny
Cos(x-y) = CosxCosy + SinxSiny
Sin2x = 2SinxCosx = 2tanx/(1+tan²x)
Cos2x = Cos²x - Sin²x = 2Cos²x-1
             =1-2Sin²x= (1-tan²x)/(1+2tan²x)
tan2x = 2tanx/(1-tan²x)
Sin3x =3Sinx - 4Sin³x
Cos3x = 4Cos³x - 3Cosx
tan3x = (3tanx-tan³x)/(1-3tan²x)