How do you find the exact value of $cos (- 225)$ $cos(-225)$ ?

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Answer 1 · 2018-03-30T20:46:04

$- \frac{\sqrt{2}}{2}$ $-sqrt2/2$

$cos (- 225) = cos (- 45 - 180) = - cos (- 45) = - cos 45 = - \frac{\sqrt{2}}{2}$ $cos (-225) = cos (-45 - 180) = -cos (-45) = -cos 45 = - sqrt2/2$

How do you find the exact value of cos(-225)cos(−225)cos(-225)?