// 2.21
clc;
th1=30;
th2=60;
th0=th1+th2/2;
Rth1=4.8;
Rth2=6.2;
Rth0=5.5;
ath0=(1/Rth0)*(Rth2-Rth1)/(th2-th1);
printf("\n alpha at o degree= %.4f /degree C ",ath0)
disp('5.5[1+0.0085(th-45)]')