cos(β−γ)+cos(γ−α)+cos(α−β)=−23⇒2[cos(β−γ)+cos(γ−α)+cos(α−β)]+3=0⇒2[cos(β−γ)+cos(γ−α)+cos(α−β)]+sin2α+cos2α+sin2β+cos2β+sin2γ+cos2γ=0⇒(sinα+sinβ+sinγ)2+(cosα+cosβ+cosγ)2=0
Let A and B denote the statements A: cos α+cos β+cos γ=0 B: sin α+sin β+sin γ=0 If cos (β-γ)+cos (γ-α)+cos (α-β)=- 3 2, then
JEE Main 2009 — Mathematics Algebra
Let A and B denote the statements A: cosα+cosβ+cosγ=0 B: sinα+sinβ+sinγ=0 If cos(β−γ)+cos(γ−α)+cos(α−β)=−23, then
Held on 30 Apr 2009 · Verified 6 Jul 2026.
Options
- A
A is true and B is false
- B
A is false and B is true
- C
both A and B are true
- D
both A and B are false
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