What is the value of $cos(-pi/4)$ ?

Question

24140 views around the world

You can reuse this answer
Creative Commons License

Answer 1 · 2016-05-27T00:39:49

$sqrt2/2$

$-pi/4$ is the same a $(11pi)/4$

This is a $45^o$ with respect to the $x-$ axis.

This angle is in the $IV$ quadrant where $cos$ is $+$

The $cos$ of a $45^o$ and is $sqrt2/2$

What is the value of cos(-pi/4)cos(-pi/4)?