If angle (theta) is 135o, evaluate cos(theta)

A.
(frac{1}{2}) 
B.
(frac{sqrt{2}}{2}) 
C.
(frac{sqrt{2}}{2}) 
D.
(frac{1}{2})
Correct Answer: Option C
Explanation
(theta) = 135o
Cos 135o = Cos(90 + 45)o
= cos90ocos45o – sin90osin45o
= 0cos45o – (1 x (frac{sqrt{2}}{2}))
= (frac{sqrt{2}}{2})
There is an explanation video available below.