cos(m+b) = cos(m-(-b)) sin(m+b) = sin(m-(-b))
sin(m+b) = sin(m-(-b))
sin(m + b) = sinmcosb + cosmsinb cos(m + b) = cosmcosb - sinmsinb
sin(m + b) = sinmcosb + cosmsinb
cos(m + b) = cosmcosb - sinmsinb