if cos theta - sin theta =1 , cos theta +sin theta =? Share with your friends Share 1 Anuradha Sharma answered this cosθ-sinθ=1squaring, we get cos2θ+sin2θ-2cosθsinθ=11-2cosθsinθ=1cosθsinθ=0.....1So cosθ+sinθ=cosθ-sinθ2+4cosθsinθ=12+4×0=1 1 View Full Answer