Given Tan (π / 4 + a) = 3, find the value of sin2a-2cos square a

Tan π / 4 = 1tan (π / 4 + a) = (Tan π / 4 + Tana) / (1-tan π / 4tana) = (1 + Tana) / (1-tana) = 3tana = 1 / 2sina / cosa = 1 / 2cosa = 2sina to substitute the identity Sin & sup2; a + cos & sup2; a = 1sin & sup2; a = 1 / 5cos & sup2; a = 4 / 5sin2a = 2sinacosa = 2sina * 2sina = 4sin & sup2

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1. Find the value of sin2a-2cos ^ 2a-1 with known Tan (π / 4 + a) = 3 I've worked out Tana = 1 / 2 In addition, sin2a-cos2a-1 is reduced to sin2a-cos2a-1-1
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