দেওয়া আছে,
$a:b=b:c$ বা, $\frac{a}{b}=\frac{b}{c}$ বা, $b^2=ac$
Left Hand Side,
$\frac{a}{c}$
Right Hand Side,
$\frac{a^2+b^2}{b^2+c^2}$
$=\frac{a^2+b^2}{b^2+c^2}$
$=\frac{a^2+ac}{ac+c^2}$
$=\frac{a\left(a+c\right)}{c\left(a+c\right)}$
$=\frac{a}{c}$
$\therefore$ Left hand Side $=$ Right Hand Side
অর্থাৎ, $\frac{a}{c}=\frac{a^2+b^2}{b^2+c^2}$ [প্রমাণিত]