7) Find the exact value of the trig function. Don't forget. to rationalize any denominators. sec 8 (-√15,7)

Holt Mcdougal Larson Pre-algebra: Student Edition 2012
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Author:HOLT MCDOUGAL
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### Trigonometry - Finding Exact Values

#### Problem
"Find the exact value of the trig function. Don’t forget to rationalize any denominators."

#### Diagram Explanation

The diagram presents a coordinate system with the \(x\)-axis and \(y\)-axis. A point \((- \sqrt{15}, 7)\) on the coordinate system is indicated, located in the second quadrant. From the origin, a vector points towards this coordinate, showing the direction of the angle \(\theta\). The vector forms an angle \(\theta\) with the positive \(x\)-axis, sweeping counter-clockwise, depicted by a red arc.

Please proceed to solve for the secant (\(\sec\)) of \(\theta\) using the provided coordinates. The solution involves the following steps:

1. **Identify \(x\) and \(y\):**
   \[
   x = -\sqrt{15}, \quad y = 7
   \]
   
2. **Find the hypotenuse \(r\):**

   Using the Pythagorean theorem for a right-angled triangle:
   \[
   r = \sqrt{x^2 + y^2} = \sqrt{(\sqrt{15})^2 + 7^2} = \sqrt{15 + 49} = \sqrt{64} = 8
   \]

3. **Calculate \(\sec \theta\):**
   \[
   \sec \theta = \frac{r}{x} = \frac{8}{-\sqrt{15}} = -\frac{8}{\sqrt{15}}
   \]

4. **Rationalize the denominator:**
   \[
   -\frac{8}{\sqrt{15}} \times \frac{\sqrt{15}}{\sqrt{15}} = -\frac{8\sqrt{15}}{15}
   \]

Thus, the exact value of \(\sec \theta\) is:
\[
\sec \theta = -\frac{8\sqrt{15}}{15}
\]

Remember, rationalizing the denominator is a crucial step in expressing trigonometric functions.
Transcribed Image Text:### Trigonometry - Finding Exact Values #### Problem "Find the exact value of the trig function. Don’t forget to rationalize any denominators." #### Diagram Explanation The diagram presents a coordinate system with the \(x\)-axis and \(y\)-axis. A point \((- \sqrt{15}, 7)\) on the coordinate system is indicated, located in the second quadrant. From the origin, a vector points towards this coordinate, showing the direction of the angle \(\theta\). The vector forms an angle \(\theta\) with the positive \(x\)-axis, sweeping counter-clockwise, depicted by a red arc. Please proceed to solve for the secant (\(\sec\)) of \(\theta\) using the provided coordinates. The solution involves the following steps: 1. **Identify \(x\) and \(y\):** \[ x = -\sqrt{15}, \quad y = 7 \] 2. **Find the hypotenuse \(r\):** Using the Pythagorean theorem for a right-angled triangle: \[ r = \sqrt{x^2 + y^2} = \sqrt{(\sqrt{15})^2 + 7^2} = \sqrt{15 + 49} = \sqrt{64} = 8 \] 3. **Calculate \(\sec \theta\):** \[ \sec \theta = \frac{r}{x} = \frac{8}{-\sqrt{15}} = -\frac{8}{\sqrt{15}} \] 4. **Rationalize the denominator:** \[ -\frac{8}{\sqrt{15}} \times \frac{\sqrt{15}}{\sqrt{15}} = -\frac{8\sqrt{15}}{15} \] Thus, the exact value of \(\sec \theta\) is: \[ \sec \theta = -\frac{8\sqrt{15}}{15} \] Remember, rationalizing the denominator is a crucial step in expressing trigonometric functions.
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