SA3 marksYear: 2024HardCBSE Class 10
trigonometrytrigonometric-identitiesproof
Question
Prove that sinθ+cosθ−1sinθ−cosθ+1=secθ−tanθ1
Solution
1
LHS =sinθ+cosθ−1sinθ−cosθ+1. Dividing numerator and denominator by cosθ: =tanθ+1−secθtanθ−1+secθ
+1 mark2
=(tanθ−secθ)+1(tanθ+secθ)−1=(tanθ−secθ)+1(tanθ+secθ)−(sec2θ−tan2θ)
+1 mark3
=(tanθ−secθ+1)(tanθ+secθ)(1−secθ+tanθ)=tanθ+secθ=secθ−tanθ1 = RHS
+1 mark