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3. Trigonometric Functions : Positive and negative angles. Measuring angles in radians and in degrees and conversion from one measure to another. Definition of trigonometric functions with the help of unit circle. Truth of the identity sin2x + cos2x = 1, for all x. Signs of trigonometric functions. Domain and range of trigonometric functions and their graphs. Expressing sin (x±y) and cos (x±y) in terms of sinx, siny, cosx & cosy and their simple applications. Deducing identities like the following: tan(x ± y) = tan x ± tan y 1 ∓ tan x tan y , cot(x ± y) = cot x cot y ∓ 1 cot y ± cot x sinα ± sinβ = 2sin 1 2 (α ± β)cos 1 2 (α ∓ β) cosα + cosβ = 2cos 1 2 (α + β)cos 1 2 (α − β) ???????????????? − ???????????????? = −2???????????? 1 2 (???? + ????)???????????? 1 2 (???? − ????) Identities related to sin2x, cos2x, tan2 x, sin3x, cos3x and tan3x.