Question 38Triangle $ABC$ is inscribed in a semicircle of radius $r$ so that its base $AB$ coincides with diameter $AB.$ Point $C$ does not coincide with either $A$ or $B.$ Let $s=AC+BC.$ Then, for all permissible positions of $C:$$s^2\le8r^2$$s^2=8r^2$$s^2\ge8r^2$$s^2\le4r^2$$s^2=4r^2$