use reference angle to find the exact value of the expression, do not use a calculator cos 225 degrees

asked Mar 14, 2023 187k views

4 votes

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4 votes

To find

$\cos 225^o$

Now,

$\begin{gathered} \cos 225^o=\cos (180^o+45^o)^{} \\ =\cos (2*90^o+45^o) \\ =-\cos 45^o \\ =-\frac{1}{\sqrt[]{2}} \end{gathered}$

So, the required value is

$-\frac{1}{\sqrt[]{2}}$

Nevermore answered Mar 19, 2023

3.5k points

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