定义在R上的函数$f\left(x\right)$既是奇函数又是周期函数，若$f\left(x\right)$的最小正周期是$\mathrm{\pi }$，且当$x\in (0,\frac{\mathrm{\pi }}{2}$时， $f\left(x\right)=\cos x$，则$f\left(\frac{5\mathrm{\pi }}{3}\right)$的值为 （  ）

Last term,Peter was ____ at home.His parents were doing busines in another city. He felt lonely,so he often turned on the computer and played computer ____. However, sitting in front of the computer for a long time is ____ for him. And he spent little time on his study.He failed his exams.Luckily,his parents ____ his problem in time.They decided to come back home.Peter studies hard now.So far,he has made progress in his study.He ____ he can catch up with his classmates soon.