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प्रश्न
Solve the following equations:
cos 2θ = `(sqrt(5) + 1)/4`
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उत्तर
We know cos 36° = `(sqrt(5) + 1)/4`, 36° = `pi/5`
cos 2θ = cos 36° = `cos (pi/5)`
The general solution is
2θ = `2"n"pi +- pi/5`, n ∈ Z
θ = `"n"pi +- pi/10`, n ∈ Z
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