If sin ( theta + alpha) = cos ( theta + alpha), prove that tan theta = (1- tan alpha) /(1+ tan alpha) Share with your friends Share 14 Varun.Rawat answered this We have, sinθ+α = cosθ+α⇒sinθ+αcosθ+α = 1⇒tanθ+α = 1⇒tan θ + tan α1 - tan θ . tan α = 1⇒1 - tan θ . tan α = tan θ + tan α⇒tan θ + tan θ . tan α = 1 - tan α⇒tan θ1 + tan α = 1 - tan α⇒tan θ = 1 - tan α1 + tan α 53 View Full Answer