[tex]\text{Apply Pythagorean theorem,}\\ \\~~~~~~12^2 = 3^2 + h^2\\\\\implies h^2 = 12^2 -3^2\\\\\implies h^2 = 144-9\\\\\implies h^2 = 135\\\\\implies h = \sqrt{135}\\\\\implies h = 3\sqrt{15}\\\\\implies h \approx 11.62[/tex]
