___________ is known to all that Shenzhou VI was launched successfully.
如下图,矩形OABC内的阴影部分由曲线f(x)=sinx(x∈(0,π))及直线x∈a(a∈(0,π))与x轴围成,向矩形OABC内随机投掷一点,若落在阴影部分的概率为316,则a的值为( )