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please give trignometric identities?
tan t =  sin t / cos t         
cot t = 1 / tan t =      cos t / sin
sec t = 1/ cos t       
cosec t = 1/ sin t

The Pythagorean formula for sines and cosines.

    sin2 t + cos2 t = 1

Identities expressing trig functions in terms of their complements

    cos t = sin( pi/2 – t)       sin t = cos( pi/2 – t)

    cot t = tan( pi/2 – t)       tan t = cot( pi/2 – t)

    csc t = sec( pi/2 – t)       sec t = csc( pi/2 – t)

Periodicity of trig functions. Sine, cosine, secant, and cosecant have period 2 pi while tangent and cotangent have period pi.

    sin (t + 2 pi) = sin t

    cos (t + 2 pi) = cos t

    tan (t + pi) = tan t

Identities for negative angles. Sine, tangent, cotangent, and cosecant are odd functions while cosine and secant are even functions.

    sin  –t = –sin t

    cos –t = cos t

    tan –t  = –tan t

Sum formulas for sine and cosine

    sin (s + t) = sin s cos t + cos s sin t

    cos (s + t) = cos s cos t – sin s sin t

Double angle formulas for sine and cosine

    sin 2t = 2 sin t cos t

    cos 2t = cos2 t – sin2 t = 2 cos2 t – 1 =  1 – 2 sin2 t


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