The inductive formula sin (-a) =-sin (a) cos (-a) = cos (a) sin (pi/2-a) = cos (a) cos (pi/2-a) = sin (a) sin (pi/2+a) = cos (a) cos (. Sin (pi+a) =-sin (a) cos (pi+a) =-cos (a) TGA = tana = Sina/COSA trigonometric function sin (a+b) = sin (a) cos (b)+cos (α) sin (b) = sin (a) cos. 1 sin(b)= 2 cos((a+b)/2)sin((a-b)/2)cos(a)+cos(b)= 2 cos((a+b)/2)cos(a ^ 2 *[cos(a+b)-cos(a-b)]cos(a)cos(b)= 1/2 *[cos(a+b)+cos(a-b)]sin(a)cos(b)= 1。 = cos2 (a)-sin2 (a) = 2cos2 (a)-1=1-2sin2 (a) half-angle formula sin2 (a/2) = (1-cos (a)) sin (a) = sin. 2)/(1+tan2 (a/2)) cos (a) = (65444 hyperbolic function sinh (a) = (ea-e (-a))/2cosh (a) = (ea+e (-a))/2tgh (.