Which of the following expressions is equal to cos125°?-cos55°cos55°cos(-55)°
Accepted Solution
A:
Answer: -cos(55°)Step-by-step explanation:The reference angle for second-quadrant angle 125° is (180-125)° = 55°. The cosine is negative in the second quadrant, so the equivalent expression is ... cos(125°) = -cos(55°)_____Your calculator (in degrees mode) can help you sort this out.