BASIC TRIGONOMETRY REFERENCE Trigonometric functions denote the relationship between the subtended angle 'x' within a right-triangle and the ratio of its sides: /| sin(a) = y/r r / | cos(a) = x/r (hyp) / | y tan(a) = y/x / | (opp) /a)__| x (adj) A triangle with hypotenuse (hyp) of unit-one length: /| / | sin(a) = sin(a)/1 1 / | sin(a) cos(a) = cos(a)/1 / | tan(a) = sin(a)/cos(a) /a)__| cos(a) Via Pythagoras' theorem, sin^2(a)+cos^2(a) = 1. USEFUL IDENTITIES: sin(a) = cos(90 - a) cos(a) = sin(90 - a) 1/sin(a) = csc(a) 1/cos(a) = sec(a) 1/tan(a) = cot(a) sin(-a) = -sin(a) csc(-a) = -csc(a) cos(-a) = cos(a) sec(-a) = sec(a) tan(-a) = -tan(a) cot(-a) = -cot(a) sin(a -/+ b) = sin(a)*cos(b) -/+ cos(x)*sin(y) -- sign at right side is at left side cos(a +/- b) = cos(x)*cos(b) -/+ sin(x)*sin(y) -- sign at left and right are opposite tan(a) +/- tan(b) tan(x +/- b) = ------------------- 1 -/+ tan(a)*tan(b) ******************************************************************* END By Navid