The diagonals of a rhombus are 12 cm and 7 cm. find the size of the smaller angle of the rhombus

The diagonals of a rhombus intersect each other at the midpoints and they are also perpendicular . So  at the smallest  angle  we have a right angled triangle with legs 6 and 3.5. Also this smallest angle  (x) is bisected by the diagonal. 
so we have:-

tan (x/2)  =  3.5 / 6

x/2 =  30.256 degrees

x = 60.51  degrees to nearest hundderth