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Sunday, 01 March 2026
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If angle \(\theta\) is 135o, evaluate cos\(\theta\)

If angle \(\theta\) is 135o, evaluate cos\(\theta\)
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  • 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 \(\frac{\sqrt{2}}{2}\))
= \(-\frac{\sqrt{2}}{2}\)

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