Question
Given that 'θ' is an angle less than 120°, what is the
value of 'θ' if it satisfies the equation 7cos² θ = 1 + sin²θ?Solution
Given, 7cos²θ = 1 + sin²θ Or 7cos²θ - sin² θ = 1 Or 7cos²θ - (1 - cos²θ) = 1 Or 8cos²θ = 2 Or cos²θ = (2/8) =1/4 Or cosθ = 1/2 (Since, in options maximum value of 'θ' is 90°therefore, we will take the positive root only) Or cosθ = cos60° θ=60°
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