设f(x,y)在Oxy平面上连续,且f(0,0)=a,试求lim1/πt^2∫∫f(x,y)dxdy,其中Dx^2+y^2≤t^2

设f(x,y)在Oxy平面上连续,且f(0,0)=a,试求lim1/πt^2∫∫f(x,y)dxdy,其中Dx^2+y^2≤t^2 设f(x)在[a,b]上连续,且a 设f(x)在[a,b]上连续,且a 设f(x)在[a,b]上连续,且a 设函数y=f(x)在[0,1]上连续,且0 设函数y=f(x)在[0,1]上连续,且0 6.设z=f(x,y)在全平面上有定义,且有连续的一阶偏导数,满足方程 6.设z=f(x,y)在全平面上有定义,且有连续的一阶偏导数,满足方程 设y=f(x)在[a,b]上连续,且f(x)≥0.证明：当且仅当f(x)≡0时, 设函数f(x)在[a,b]上连续,在(a,b)内可导且f'(x) 设函数f(x)在[a,b]上连续,在(a,b)上可导且f'(x) 设y=f(x)在[a,正无穷]上连续,且x趋于正无穷时,f(x)存在,证明:f在[a,正无穷]上有界 设f(x)在[0,1]上具有二阶连续导数,且|f''(x)| 设f(x)在[0,1]上连续,且f(x) 设函数f(x),g(x)在区间[a,b]上连续,且f(a) 高等数学问题：设f(x)在[0,1]上连续,且f(x) 设函数y=f(x)在[a,b]上连续且单调,证明其反函数在相应区间上也连续且单调 设f(x)在区间[0,1]上连续,且f0)f(1)