in triangle abc a=12 b=16 and sinB=2/3 what is the measure of angle A in degrees
还有：
the equation x^2+2ix-4=0 has as its toot
a根号下5-1,-根号下5-1
b根号下5-i,根号下5+i
c根号下3-i,根号下5+i
d根号下3-i,根号下3+i
e根号下3-1,-根号下3-i