Question 1036513

Find the exact value of cos(pi) cos(3pi/4) + sin(pi) sin (3pi/4)
<pre>This represents the COSINE Difference of 2 angles, as follows: {{{cos (A - B) = cos (A) cos (B) + sin (A) sin (B)}}}
{{{highlight_green(cos (pi) cos (3pi/4) + sin (pi) sin (3pi/4) = cos (pi - 3pi/4) = cos ((4pi - 3pi)/4) = cos (pi/4) = highlight(highlight_green(highlight(sqrt(2)/2))))}}}