Answer
Distance between points $(a,0) $and $(0,b)$ is-
$\sqrt{a^{2} + b^{2}} $ unit
Work Step by Step
Distance 'd' between two points $(x_{1},y_{1}) $ and $(x_{2},y_{2})$ is given by-
d = $\sqrt{(x_{1} - x_{2})^{2} + (y_{1} - y_{2})^{2}} $
Therefore, distance '$d$' between points $(a,0) $and $(0,b)$ will be -
d = $\sqrt{(a - 0)^{2} + (0 - b)^{2}} $
i.e. d = $\sqrt{a^{2} + b^{2}} $ unit