JAMB - Mathematics (2012 - No. 28)
If angle \(\theta\) is 135o, evaluate cos\(\theta\)
\(\frac{1}{2}\)
\(\frac{\sqrt{2}}{2}\)
\(-\frac{\sqrt{2}}{2}\)
\(-\frac{1}{2}\)
คำอธิบาย
\(\theta\) = 135o
Cos 135o = Cos(90 + 45)o
= cos90ocos45o - sin90osin45o
= 0cos45o - (1 x \(\frac{\sqrt{2}}{2}\))
= \(-\frac{\sqrt{2}}{2}\)
Cos 135o = Cos(90 + 45)o
= cos90ocos45o - sin90osin45o
= 0cos45o - (1 x \(\frac{\sqrt{2}}{2}\))
= \(-\frac{\sqrt{2}}{2}\)