紧急求助！！！ discount, actual, effective

zty999

求助胡老师
The actual discount on the 60-day T-bills 0.08867 (60/360) = 0.014778,
 so the effective 60-day yield is 1/(1 -0.014778) -1 = 1.5%.
这第二个式子用的是什么公式啊？看不懂