Question

How to find the value of
Cos 135 degrees?

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Answer 1

Answer:

$\sf{cos \: 135 \degree \: can\: be\: written\: as\: cos(180-45)}$

$\implies \sf{cos (180-45)}$

$\implies\sf{= - cos 45}$

$\implies \sf \boxed{- \frac{1}{ \sqrt{2} }}$

Note →

$\sf \bf{cos (180-\theta) = -cos \theta}$

$\mathscr{\large{Thanks}}\heartsuit$

Answer 2

$\large \sf \underline{ \underline{ \: Solution : \: \: \: }}$

$\implies \sf Cos \: (135) \\ \\ \implies \sf</p><p>Cos \: (90 + 45) \\ \\ \implies \sf </p><p>- Sin \: (45) \\ \\ \implies \sf </p><p>- \frac{1}{ \sqrt{3} } </p><p>$

$\large \sf \underline{ \underline{ \: Remmember \: \: \: }}$

$\star \: \: \sf Cos \: (90 + \theta) = - Sin \: ( \theta)$