Đặt \(sinx=t\left(t\in\left[-1;1\right]\right)\)
Khi đó \(y=f\left(t\right)=t^2-4t+5\)
\(M=maxf\left(t\right)=max\left\{f\left(-1\right);f\left(1\right)\right\}=f\left(-1\right)=10\)
\(m=min\left(t\right)=min\left\{f\left(-1\right);f\left(1\right)\right\}=f\left(1\right)=2\)
\(\Rightarrow P=M-2m^2=10-2.4=2\)