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Question Number 159787 by abdullah_ff last updated on 21/Nov/21
if cos^4 θ − sin^4 θ = 2 − 5cosθ  then find the value of θ
ifcos4θsin4θ=25cosθthenfindthevalueofθ
Commented by cortano last updated on 21/Nov/21
⇒ cos^2 θ−sin^2 θ−2+5cos θ = 0  ⇒cos^2 θ−1+cos^2 θ−2+5cos θ= 0   ⇒2cos^2 θ+5cos θ−3 = 0  ⇒(2cos θ−1)(cos θ+3)=0  ⇒cos θ=(1/2) ⇒θ=± (π/3)+2nπ
cos2θsin2θ2+5cosθ=0cos2θ1+cos2θ2+5cosθ=02cos2θ+5cosθ3=0(2cosθ1)(cosθ+3)=0cosθ=12θ=±π3+2nπ
Commented by abdullah_ff last updated on 23/Nov/21
thank you sir
thankyousir

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