The square on the hypotenuse is skew and impossible to visually validate. There's nothing to sum. It is a simple calculation to note that <span><span><span>32</span>+<span>42</span>=<span>52</span></span><span><span>32</span>+<span>42</span>=<span>52</span></span></span><span>, but its picture doesn't 'say' that the angle between the 3 and 4 sided square must be 90 degrees.
