cos-1125°=cos1125° [Since, cos-x=cosx]=cos1080°+45° [360°×3=1080° or 6π]=cos-45° [Since, cos3π+x=cos-x]=cos45° [Since, cos-x=cosx]=12

EVALUATE cos(-1125)

\cos (- 1125 °) = \cos (1125 °) [S i n c e, \cos (- x) = \cos (x)] = \cos (1080 ° + 45 °) [360 ° \times 3 = 1080 ° o r 6 π] = \cos (- 45 °) [Since, \cos (3 π + x) = \cos (- x)] = \cos (45 °) [S i n c e, \cos (- x) = \cos (x)] = \frac{1}{\sqrt{2}}