Check sibling questions

(sec A + tan A) (1 – sin A) equals:

(a) sec A                        (b) sin A                   (c) cosec A               (d) cos A

This question is similar to Example 10 - Chapter 8 Class 10 Introduction to Trignometry

Slide27.JPG

Slide28.JPG

Learn in your speed, with individual attention - Teachoo Maths 1-on-1 Class


Transcript

(sec A + tan A)(1 – sin A) We write everything in terms of sin A and cos A = (1/cos⁑〖 𝐴〗 +" " sin⁑〖 𝐴〗/cos⁑〖 𝐴〗 ) (1 – sin A) = ((1 +γ€– sin〗⁑〖 𝐴〗)/cos⁑〖 𝐴〗 )(1 – sin A) = ((1 +γ€– sin〗⁑〖 𝐴) (1 βˆ’γ€– sin〗⁑〖 𝐴)γ€— γ€—)/(cos⁑ 𝐴 ) = ((12 βˆ’γ€– sin^2〗⁑〖 𝐴) γ€—)/( cos⁑〖 𝐴〗 ) = ((𝟏 βˆ’γ€– γ€–π’”π’Šπ’γ€—^πŸγ€—β‘γ€– 𝑨) γ€—)/( 𝒄𝒐𝒔⁑〖 𝑨〗 ) = cos⁑〖2 𝐴〗/( cos⁑〖 𝐴〗 ) = cos A cos2 A + sin2 A = 1 cos2 A = 1 – sin2 A ∴ 1 – sin2 A = cos2 A So, the correct answer is (d)

Ask a doubt
Davneet Singh's photo - Co-founder, Teachoo

Made by

Davneet Singh

Davneet Singh has done his B.Tech from Indian Institute of Technology, Kanpur. He has been teaching from the past 13 years. He provides courses for Maths, Science, Social Science, Physics, Chemistry, Computer Science at Teachoo.