Odpowiedź:
r = [tex]\frac{9\sqrt{7} }{7}[/tex]
Wyjaśnienie:
Dane:
a = 18 cm
b = 12 cm
c = 12 cm
p=[tex]\frac{a+b+c}{2}[/tex]
p = [tex]\frac{18+12+12}{2} =\frac{42}{2} =21[/tex]
r = [tex]\sqrt{\frac{(p-a)(p-b)(p-c)}{p} }[/tex]
r = [tex]\sqrt{\frac{(21-18)(21-12)(21-12)}{21} } = \sqrt{\frac{3*9*9}{21} } =\sqrt{\frac{243}{21} } =\sqrt{\frac{81}{7} } =\frac{9\sqrt{7} }{\sqrt{7}*\sqrt{7} } =\frac{9\sqrt{7} }{7}[/tex]
