Trigonometry 7th Edition

$140^{\circ}$
First, ensure that your calculator is in radians. On your graphing calculator, press the following sequence of buttons: 1. COS$^{-1}$ 2. ( 3. -.766 4. ) 5. ENTER Therefore, $cos^{-1}(-.766)=2.443$ radians. Then, convert this number to degrees by multiplying by $\frac{180}{\pi}$. $2.443radians=(2.443(\frac{180}{\pi}))^{\circ}=140^{\circ}$.