# Misc. 15 - Chapter 4 Class 12 Determinants (Term 1)

Last updated at Jan. 23, 2020 by Teachoo

Last updated at Jan. 23, 2020 by Teachoo

Transcript

Misc 15 Using properties of determinants, prove that: |■8(sinα&cosα&cos〖(α+δ)〗@sinβ&cosβ&cos〖(β+δ)〗@sinγ&cosγ&cos〖(γ+δ)〗 )| = 0 Let ∆ = |■8(sinα&cosα&cos〖(α+δ)〗@sinβ&cosβ&cos〖(β+δ)〗@sinγ&cosγ&cos〖(γ+δ)〗 )| Using cos (x + y) = cos x cos y – sin x sin y = |■8(sinα&cosα&cos𝛼 cos〖δ −sin〖𝛼 sin𝛿 〗 〗@sinβ&cosβ&cos𝛽 cos〖𝛿−sin〖𝛽 sin𝛿 〗 〗@sinγ&cosγ&cosγcos 𝛿 −sin〖γ sin𝛿 〗 )| Expressing elements of 2nd row as sum of two elements = |■8(sinα&cosα&cos 𝛼 cos〖δ 〗@sinβ&cosβ&cos𝛽 cos𝛿@sinγ&cosγ&cos γ cos 𝛿 )| + |■8(sinα&cosα&−sin〖𝛼 sin𝛿 〗@sinβ&cosβ&−sin〖𝛽 sin𝛿 〗@sinγ&cosγ&−sin〖γ sin𝛿 〗 )| Using Property : If some or all elements of a row or column of a determinant are expressed as sum of two (or more) terms ,then the determinant is expressed as a sum of two (or more) determinants. Taking cos 𝛿 common from C3 = cos〖δ 〗 |■8(sinα&cosα&cos 𝛼@sinβ&cosβ&cos𝛽@sinγ&cosγ&cos γ )| + (−sin𝛿) |■8(sinα&cosα&sin𝛼@sinβ&cosβ&sin𝛽@sinγ&cosγ&sinγ )| = cos〖δ 〗(0) + (−sinδ) (0) = 0 = R.H.S Hence proved Using Property: If any two row or column are identical, then value of determinant is zero

Miscellaneous

Misc 1

Misc. 2 Important Deleted for CBSE Board 2022 Exams

Misc 3

Misc 4 Deleted for CBSE Board 2022 Exams

Misc 5

Misc 6 Important Deleted for CBSE Board 2022 Exams

Misc 7 Important

Misc 8

Misc 9

Misc 10

Misc 11 Important Deleted for CBSE Board 2022 Exams

Misc 12 Important Deleted for CBSE Board 2022 Exams

Misc. 13 Deleted for CBSE Board 2022 Exams

Misc 14 Deleted for CBSE Board 2022 Exams

Misc. 15 Important Deleted for CBSE Board 2022 Exams You are here

Misc. 16 Important

Misc 17 Important Deleted for CBSE Board 2022 Exams

Misc 18

Misc 19 Important

Matrices and Determinants - Formula Sheet and Summary

Chapter 4 Class 12 Determinants (Term 1)

Serial order wise

About the Author

Davneet Singh

Davneet Singh is a graduate from Indian Institute of Technology, Kanpur. He has been teaching from the past 10 years. He provides courses for Maths and Science at Teachoo.