證明曲線x^2/3+y^2/3=a^2/3(注a>0常數,2/3為次方)上任意點處的切線介於兩坐標軸之間的線段長為定長

證明曲線x^2/3+y^2/3=a^2/3(注a>0常數,2/3為次方)上任意點處的切線介於兩坐標軸之間的線段長為定長

記a^(2/3)=A,原式可化為:y=[A-x^(2/3)]^(3/2)=f(x)對x求導:y=[A-x^(2/3)]^(1/2)*[-x^(-1/3)]=-[f(x)]^(1/3)*x^(-1/3)故(m,n)處切線為:y=-n^(1/3)*m^(-1/3)(x-m)+n令x=0,y=n^(1/3)*A令y=0,x=m^(1/3)*A介於坐標軸間的…