You want to find the measure of angle x. Rearrange the given 8 cos x+3=0 as <span>8 cos x= -3, or cos x = -3 / 8, or cos x = -0.375.
Use the arccos function (inverse cosine) to find the value of x in radians and in degrees.
Since the cosine function is negative only in Quadrants II and III, focus on the following possible ranges: Quadrant II: 90 < x < 180 and Quadrant III: 180 < x < 270.
Example: using my calculator to obtain the inverse cosine of -0.375, I got x = 1.96 radians. Convert this into degrees if desired. Draw a ray showing this angle. Reflect this ray across the horiz. axis to obtain the angle in Q III.</span>
