Question 972825
Start with the unit vector of the unit circle
at 0 degrees
Then rotate 360 degrees back to where you started
Then rotate 45 degrees more.
{{{ 360 + 45 = 405 }}}
You are in the 1st quadrant where the cosine is positive
{{{ cos( 405 ) = cos( 45 ) }}}
{{{ cos( 405 ) = sqrt(2) / 2 }}}