Compute: {{MATH_147}} {{CMD_148}} The issue here is that {{MATH_149}} might not be in the range of arccosine. To find our missing number, we'll check with a unit circle that we've decorated with the domain of arccosine: {{CMD_150}} {{ENV_151}} {{CMD_152}} Since the points {{MATH_153}} and {{MATH_154}} have the same {{MATH_155}}-coordinate, {{MATH_156}}. Hence {{MATH_157}} {{CMD_158}} {{CMD_159}}