a: MN/MP=3/4 nên IN/IP=9/16
=>IN=9/16IP
Ta có: \(MI^2=IN\cdot IP\)
=>\(\dfrac{9}{16}IP^2=9.6^2\)
=>IP=12,8(cm)
=>IN=7,2(cm)
\(MN=\sqrt{7.2\cdot20}=12\left(cm\right)\)
\(MP=\sqrt{12.8\cdot20}=16\left(cm\right)\)
NP=7.2+12.8=20cm
b: \(S_{MIP}=\dfrac{9.6\cdot12.8}{2}=9.6\cdot6.4=61.44\left(cm^2\right)\)