If   $\displaystyle {\cos{\alpha}}={0.312}$   and   $\displaystyle {\cos{\beta}}={0.914}$   with both angles’ terminal rays in Quadrant-I, find the values of
(a)
$\displaystyle {\cos{{\left(\alpha+\beta\right)}}}=$
(b)
$\displaystyle {\sin{{\left(\alpha+\beta\right)}}}=$
Your answers should be accurate to 4 decimal places.