sin(theta) = a / ccsc(theta) = 1 / sin(theta) = c / a

cos(theta) = b / csec(theta) = 1 / cos(theta) = c / b

tan(theta) = sin(theta) / cos(theta) = a / bcot(theta) = 1/ tan(theta) = b / a

sin(-x) = -sin(x)csc(-x) = -csc(x)cos(-x) = cos(x)sec(-x) = sec(x)tan(-x) = -tan(x)cot(-x) = -cot(x)sin2(x) + cos2(x) = 1tan2(x) + 1 = sec2(x)cot2(x) + 1 = csc2(x)

sin(xy) = sin x cos ycos x sin y

cos(xy) = cos x cosysin x sin y

tan(xy) = (tan xtan y) / (1tan x tan y)sin(2x) = 2 sin x cos xcos(2x) = cos2(x) - sin2(x) = 2 cos2(x) - 1 = 1 - 2 sin2(x)tan(2x) = 2 tan(x) / (1 - tan2(x))sin2(x) = 1/2 - 1/2 cos(2x)cos2(x) = 1/2 + 1/2 cos(2x)sin x - sin y = 2 sin( (x - y)/2 ) cos( (x + y)/2 )cos x - cos y = -2 sin( (x-y)/2 ) sin( (x + y)/2 )Trig Table of Common Angles

angle030456090

sin2(a)0/41/42/43/44/4

cos2(a)4/43/42/41/40/4

tan2(a)0/41/32/23/14/0

Given Triangle abc, with angles A,B,C; a is opposite to A, b oppositite B, c opposite C:a/sin(A) = b/sin(B) = c/sin(C)(Law of Sines)c2= a2+ b2- 2ab cos(C)b2= a2+ c2- 2ac cos(B)a2= b2+ c2- 2bc cos(A)

(Law of Cosines)

(a - b)/(a + b) = tan 1/2(A-B) / tan 1/2(A+B)(Law of Tangents)