Question

In a right triangle where one angle measures 30 degrees, how do you express the secant of that angle?

Ask by Watson Ross. in South Africa
Jan 23,2025

Real Tutor Solution

Tutor-Verified Answer

Answer

\[ \sec(30^\circ) = \frac{2\sqrt{3}}{3} \]

Solution

In a right triangle with one angle measuring \(30^\circ\), you can express the secant of that angle (\(\sec(30^\circ)\)) using the side lengths of the triangle. Here's how: 1. **Understand the Triangle Ratios:** In a \(30^\circ-60^\circ-90^\circ\) right triangle, the sides are in the ratio: \[ 1 : \sqrt{3} : 2 \] - The side opposite the \(30^\circ\) angle is the shortest and is considered to be \(1\) unit. - The side opposite the \(60^\circ\) angle is \(\sqrt{3}\) units. - The hypotenuse (opposite the \(90^\circ\) angle) is \(2\) units. 2. **Define Secant:** The secant of an angle in a right triangle is defined as the ratio of the hypotenuse to the adjacent side: \[ \sec(\theta) = \frac{\text{Hypotenuse}}{\text{Adjacent side}} \] 3. **Apply to \(30^\circ\) Angle:** For the \(30^\circ\) angle: - **Hypotenuse:** \(2\) units - **Adjacent side:** \(\sqrt{3}\) units Therefore: \[ \sec(30^\circ) = \frac{2}{\sqrt{3}} \] 4. **Rationalize the Denominator (Optional):** To rationalize the denominator: \[ \sec(30^\circ) = \frac{2}{\sqrt{3}} \times \frac{\sqrt{3}}{\sqrt{3}} = \frac{2\sqrt{3}}{3} \] **Final Answer:** \[ \sec(30^\circ) = \frac{2\sqrt{3}}{3} \]

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Bonus Knowledge

In a right triangle with a 30-degree angle, the secant function can be found using the cosine of that angle. Since secant is the reciprocal of cosine, we first note that the cosine of 30 degrees is \( \frac{\sqrt{3}}{2} \). Therefore, the secant of 30 degrees is \( \sec(30^\circ) = \frac{1}{\cos(30^\circ)} = \frac{2}{\sqrt{3}} \), which can also be rationalized to \( \sec(30^\circ) = \frac{2\sqrt{3}}{3} \). Now, if you ever find yourself scratching your head over these functions, remember that the unit circle is your best friend! At 30 degrees, or \( \frac{\pi}{6} \) radians, the coordinates are \( \left(\frac{\sqrt{3}}{2}, \frac{1}{2}\right) \). This means you can always derive sine, cosine, and secant values from these simple coordinates. Who knew geometry could be such a useful, not to mention fun, puzzle?

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