//chapter8,Example8_11,pg 185

//condition for dark is 2*u*t*cos(r)=n*lam

lam=5890*10^-8

u=1.5

r=60*(%pi/180)

//for n=1

t=(lam)/(2*u*cos(r))

printf("smallest thickness of glass plate\n")

printf("t=%.8f cm",t)