1/22/20

TRIGONOMETRY FORMULA

Important formula of Trigonometry:

Wherever ‘square’ appears think of using the identities
  •  sin^2(x) + cos^2(x) = 1
  • tan^2(x) + 1 = sec^2(x)
  • cot^2(x) + 1 = csc^2(x)
  • tan(x+ y) = (tan x +tan y) / (1 – tan x tan y)
  • sin(2x) = 2 sin x cos x
  • cos(2x) = cos^2(x) – sin^2(x) = 2 cos^2(x) – 1 = 1 – 2 sin^2(x)
  • tan(2x) = 2 tan(x) / (1 – tan^2(x))
  • sin^2(x) = 1/2 – 1/2 cos(2x)
  • cos^2(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 )

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