SA3 marksYear: 2020HardCBSE Class 10
trigonometryidentitiesproof
Question
Prove that:
cosθ+sinθ−1sinθ−cosθ+1=secθ−tanθ1
Solution
1
L.H.S =cosθ+sinθ−1sinθ−cosθ+1. Dividing numerator and denominator by cosθ: =1+tanθ−secθtanθ−1+secθ
+1 mark2
=1+tanθ−secθtanθ+secθ−1. Using sec2θ−tan2θ=1: =secθ−tanθ(secθ+tanθ−1)(secθ−tan2θ)+tanθ−secθ
+1 mark3
=(secθ−tanθ)(secθ+tanθ−1)tanθ+secθ−1=secθ−tanθ1= R.H.S
+1 mark