sqrt(h^2 + w^2) (assuming height h and width w)

(drawn with hypotenuse length 5 and leg length 3)

edge lengths | w | h | sqrt(h^2 + w^2) area | (h w)/2 = 0.5 h w perimeter | sqrt(h^2 + w^2) + h + w interior angles | (sin^(-1)(w/sqrt(h^2 + w^2)) rad | sin^(-1)(h/sqrt(h^2 + w^2)) rad | π/2 rad)≈(sin^(-1)(w/sqrt(h^2 + w^2)) rad | sin^(-1)(h/sqrt(h^2 + w^2)) rad | 1.5708 rad) interior angle sum | 180° = π rad≈3.142 rad (assuming height h and width w)