Which among the choices has the correct combination of the values for sin θ, cos θ, and tan θ?

Question image

Understand the Problem

The question is asking to identify the correct set of values for the trigonometric functions sin θ, cos θ, and tan θ from a list of choices provided.

Answer

The correct combination is: $$ \sin \theta = \frac{5}{7}, \cos \theta = -\frac{2\sqrt{6}}{7}, \tan \theta = -\frac{5}{2\sqrt{6}} $$
Answer for screen readers

The correct combination of values is:

1st option: $$ \sin \theta = \frac{5}{7}, \cos \theta = -\frac{2\sqrt{6}}{7}, \tan \theta = -\frac{5}{2\sqrt{6}} $$

Steps to Solve

  1. Identify the Pythagorean Identity The relationship between sine, cosine, and tangent is given by the identity: $$ \sin^2 \theta + \cos^2 \theta = 1 $$ Additionally, the tangent is related as: $$ \tan \theta = \frac{\sin \theta}{\cos \theta} $$

  2. Calculate for Each Option For each option, check if the values of $\sin \theta$ and $\cos \theta$ satisfy the Pythagorean identity.

    • First Option:

      • $\sin \theta = \frac{5}{7}$, $\cos \theta = -\frac{2\sqrt{6}}{7}$
      • Check: $$ \left(\frac{5}{7}\right)^2 + \left(-\frac{2\sqrt{6}}{7}\right)^2 = \frac{25}{49} + \frac{24}{49} = \frac{49}{49} = 1 $$
      • Calculate $\tan \theta$: $$ \tan \theta = \frac{\frac{5}{7}}{-\frac{2\sqrt{6}}{7}} = -\frac{5}{2\sqrt{6}} $$
    • Second Option:

      • $\sin \theta = \frac{\sqrt{5}}{3}$, $\cos \theta = -\frac{2}{3}$
      • Check: $$ \left(\frac{\sqrt{5}}{3}\right)^2 + \left(-\frac{2}{3}\right)^2 = \frac{5}{9} + \frac{4}{9} = \frac{9}{9} = 1 $$
      • Calculate $\tan \theta$: $$ \tan \theta = \frac{\frac{\sqrt{5}}{3}}{-\frac{2}{3}} = -\frac{\sqrt{5}}{2} $$
    • Third Option:

      • $\sin \theta = \frac{2}{3}$, $\cos \theta = -\frac{\sqrt{11}}{2}$
      • Check: $$ \left(\frac{2}{3}\right)^2 + \left(-\frac{\sqrt{11}}{2}\right)^2 = \frac{4}{9} + \frac{11}{4} $$
      • Compute common denominator: $$ \frac{4}{9} + \frac{99}{36} \neq 1 $$
    • Fourth Option:

      • $\sin \theta = \frac{3}{4}$, $\cos \theta = -\frac{\sqrt{7}}{4}$
      • Check: $$ \left(\frac{3}{4}\right)^2 + \left(-\frac{\sqrt{7}}{4}\right)^2 = \frac{9}{16} + \frac{7}{16} = 1 $$
      • Calculate $\tan \theta$: $$ \tan \theta = \frac{\frac{3}{4}}{-\frac{\sqrt{7}}{4}} = -\frac{3}{\sqrt{7}} $$
  3. Select the Correct Option After calculations, the first, second, and fourth options satisfy the identity, and we can compare the calculated $\tan \theta$.

The correct combination of values is:

1st option: $$ \sin \theta = \frac{5}{7}, \cos \theta = -\frac{2\sqrt{6}}{7}, \tan \theta = -\frac{5}{2\sqrt{6}} $$

More Information

These values are derived using the fundamental Pythagorean identity which all sine and cosine pairs must satisfy. Ensuring accuracy in these functions is crucial in trigonometry.

Tips

  • Not checking if $\sin^2 \theta + \cos^2 \theta = 1$ for each option.
  • Miscalculating the values when applying the Pythagorean identity.

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