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If 
cos theta=(1)/(6), then what is the positive value of 
tan ((1)/(2)theta), in simplest radical form with a rational denominator?

If cosθ=16 \cos \theta=\frac{1}{6} , then what is the positive value of tan12θ \tan \frac{1}{2} \theta , in simplest radical form with a rational denominator?

Full solution

Q. If cosθ=16 \cos \theta=\frac{1}{6} , then what is the positive value of tan12θ \tan \frac{1}{2} \theta , in simplest radical form with a rational denominator?
  1. Apply double angle formula: Use the double angle formula for tangent: tan(12θ)=±1cos(θ)1+cos(θ)\tan(\frac{1}{2}\theta) = \pm\sqrt{\frac{1 - \cos(\theta)}{1 + \cos(\theta)}}. Substitute cos(θ)=16\cos(\theta) = \frac{1}{6} into the formula. tan(12θ)=±1161+16\tan(\frac{1}{2}\theta) = \pm\sqrt{\frac{1 - \frac{1}{6}}{1 + \frac{1}{6}}}.
  2. Substitute cos(θ):\cos(\theta): Simplify the expression inside the square root.\newlinetan(12θ)=±(6616)/(66+16).\tan\left(\frac{1}{2}\theta\right) = \pm\sqrt{\left(\frac{6}{6} - \frac{1}{6}\right) / \left(\frac{6}{6} + \frac{1}{6}\right)}.\newlinetan(12θ)=±(56)/(76).\tan\left(\frac{1}{2}\theta\right) = \pm\sqrt{\left(\frac{5}{6}\right) / \left(\frac{7}{6}\right)}.
  3. Simplify expression: Simplify the fraction inside the square root by multiplying the numerator and denominator by 66.tan(12θ)=±57\tan\left(\frac{1}{2}\theta\right) = \pm\sqrt{\frac{5}{7}}.
  4. Simplify fraction: Since we are looking for the positive value, choose the positive square root. tan(12θ)=57\tan\left(\frac{1}{2}\theta\right) = \sqrt{\frac{5}{7}}.
  5. Choose positive value: Rationalize the denominator.\newlinetan(12θ)=57×77.\tan\left(\frac{1}{2}\theta\right) = \sqrt{\frac{5}{7}} \times \sqrt{\frac{7}{7}}.\newlinetan(12θ)=3549.\tan\left(\frac{1}{2}\theta\right) = \sqrt{\frac{35}{49}}.
  6. Rationalize denominator: Simplify the square root. tan(12θ)=357\tan\left(\frac{1}{2}\theta\right) = \frac{\sqrt{35}}{7}.

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