Use a calculator to evaluate and round your answer to 3 decimal places. \( \cos \left(\frac{7}{10} \pi\right)=\square \)

To evaluate \( \cos\left(\frac{7}{10}\pi\right) \) and round it to three decimal places, follow these steps: 1. **Understand the Angle:** - \( \frac{7}{10}\pi \) radians is equivalent to \( 126^\circ \) because \( \pi \) radians = \( 180^\circ \), so: \[ \frac{7}{10}\pi \times \frac{180^\circ}{\pi} = 126^\circ \] 2. **Use a Calculator:** - Enter \( 126^\circ \) into your calculator set to degree mode. - Calculate the cosine of \( 126^\circ \): \[ \cos(126^\circ) \approx -0.587785 \] 3. **Round to Three Decimal Places:** - Rounding \( -0.587785 \) to three decimal places gives: \[ -0.588 \] **Final Answer:** \[ \cos\left(\frac{7}{10}\pi\right) \approx -0.588 \]