Trig identities

• tanx = sinx/cosx
• 1/tanx =cotx = cosx/sinx
• cosecx = 1/sinx
• secx = 1/cosx
• sin^2x + cos^2x = 1
• cot^2x +1 = cosec^2x
• 1+tan^2x = sec^2x
• cos^-1x = arcosx
• sin^-1x = arcsinx
• tan^-1x = arctanx
• sin2x = 2sinxcosx
• cos2x= 2cos^2x -1

  = 1-2sin^2x

  = cos^2x - sin^2x
• tan2x = (2tanx)/(1-tan^2x)
• tan(A+/-B) = (tanA +/- tanB)/(1 -/+ tanAtanB)
• sin(A +/- B) = sinAcosB +/- cosAsinB
• cos(A +/- B) = cosAcosB -/+ sinAsinB
• sinx = approx. x
• cosx = approx. 1- 1/2x^2
• tanx = approx. x