4(1-cos²θ)-4cosθ-1=0
4cos²θ+4cosθ-3=0
(2cosθ+3)(2cosθ-1)=0
cosθ=-3/2,1/2
-3/2は-1より小さいので不適
よってcosθ=1/2
θ=60°
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4(1-cos²θ)-4cosθ-1=0
4cos²θ+4cosθ-3=0
(2cosθ+3)(2cosθ-1)=0
cosθ=-3/2,1/2
-3/2は-1より小さいので不適
よってcosθ=1/2
θ=60°
Users viewing this question
are also looking at these questions 😉
ありがとうございます😊