set term qt font 'serif,14'
set xlabel "I"
set ylabel "U"
set zlabel "R"

muU = 5
muI = 0.1

set xtics ("0" 0,"{/Symbol m}_{I}" muI)
set ytics ("0" 0,"{/Symbol m}_{U}" muU)
set ztics ("0" 0,"{/Symbol m}_{U} / {/Symbol m}_{I}" muU/muI)

splot [0:2*muI][0:2*muU][0:5*muU/muI] y/x t "R = U / I" lw 2, \
	"<echo '0.1 5 50'" w p pt 7 \
		t "({/Symbol m}_I, {/Symbol m}_U, {/Symbol m}_U / {/Symbol m}_I)", \
	muU/muI - (muU/muI**2)*(x-muI) + (y-muU)/muI t "1. řád T. r."