Find cos(225^circ ) sqrt (2) (-1)/(sqrt (2)) (1)/(sqrt (3)) -(sqrt (2))/(2)

To find , we can use the unit circle and the properties of the cosine function.The angle is in the third quadrant of the unit circle, where the cosine values are negative.We can use the reference angle to find the cosine value.The reference angle is the acute angle formed by the terminal side of and the positive x-axis.The cosine of an angle in the third quadrant is the negative of the cosine of its reference angle.So, The cosine of is .Therefore, The correct answer is .