What is the sum of the intercepts of the line whose perpendicular distance from origin is 4 units and the angle which the normal makes with positive direction of x-axis is 15^\circ?

  1. A. 8
  2. B. 4\sqrt{6}
  3. C. 8\sqrt{6}
  4. D. 16

Correct Answer: C. 8\sqrt{6}

Explanation

The equation of the line in normal form is x\cos 15^\circ + y\sin 15^\circ = 4. The x-intercept a = \frac{4}{\cos 15^\circ} and the y-intercept b = \frac{4}{\sin 15^\circ}. The sum is 4(\frac{1}{\cos 15^\circ} + \frac{1}{\sin 15^\circ}) = 4(\frac{\sin 15^\circ + \cos 15^\circ}{\sin 15^\circ \cos 15^\circ}). Using the values \sin 15^\circ + \cos 15^\circ = \frac{\sqrt{6}}{2} and \sin 15^\circ \cos 15^\circ = \frac{1}{4}, the sum evaluates to 4(\frac{\sqrt{6}/2}{1/4}) = 8\sqrt{6}.

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