in triangle abc a=12 b=16 and sinB=2/3 what is the measure of angle A in degrees

题目

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

答案

第一题：可以用正弦定理得：sinA /a=sinB /b
所以得sinA=1/2,所以angle A=30度
第二题：由韦达定理得：方程根=[（-2i±根号下（4i²+16）]/2=-i±根号下3
所以选e
希望答案能满意.