16.已知x、y均为实数,记max{x,y}=$\left\{\begin{array}{l}{x,x≥y}\\{y,x<y}\end{array}\right.$,min{x,y}=$\left\{\begin{array}{l}{y,x≥y}\\{x,x<y}\end{array}\right.$.若i表示虚数单位,且a=x1+y1i,b=x2+y2i,x1,y1,x2,y2∈R,则( )
A. | min{|a+b|,|a-b|}≤min{|a|,|b|} | B. | max{|a+b|,|a-b|}≤max{|a|,|b|} | ||
C. | min{|a+b|2,|a-b|2}≥|a|2+|b|2 | D. | max{|a+b|2,|a-b|2}≥{|a|2+|b|2 |
13.如图,在平面直角坐标系xoy中,圆x2+y2=r2(r>0)内切于正方形ABCD,任取圆上一点P,若$\overrightarrow{OP}$=m$\overrightarrow{OA}$+n$\overrightarrow{OB}$(m,n∈R),则$\frac{1}{4}$是m2,n2的等差中项,现有一椭圆$\frac{{x}^{2}}{{a}^{2}}$+$\frac{{y}^{2}}{{b}^{2}}$=1(a>b>0)内切于矩形ABCD,任取椭圆上一点P,若$\overrightarrow{OP}$=m$\overrightarrow{OA}$+n$\overrightarrow{OB}$(m,n∈R),则m2,n2的等差中项为( )
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A. | $\frac{1}{4}$ | B. | $\frac{1}{2}$ | C. | $\frac{\sqrt{2}}{2}$ | D. | 1 |