Question 149724
315 degrees is 45 degrees away from 0 degrees.
Therefore sin(315)=cos(315).
You also know that for any angle, x,
{{{sin^2(x)+cos^2(x)=1}}}
In this case,
{{{cos^2(315)+cos^2(315)=1}}}
{{{2cos^2(315)=1}}}
{{{cos^2(315)=1/2}}}
{{{cos(315)=1/sqrt(2)}}}
{{{cos(315)=sqrt(2)/2}}}