函数式y=½A·[sin(πx/6-π/2)+1]=½A·[1-cos(πx/6)]
y'=½A·π/6·sin(πx/6)=(Aπ/12)·sin(πx/6)
∫½A·[1-cos(πx/6)]dx=½Ax-(3/π)sin(πx/6)+C
