Calculate the blue shaded area

Math with Alex | Math Alex | Premath | Math Booster | Math Queen | Mathematrick | Andy Math | Magda liebt Mathe | area of a right angled triangle | right triangle area derivation | 30-60-90 triangles | isosceles triangles | interior angle sum theorem | triangle area proof | geometric derivation | Euclidean geometry | geometry proof | special triangles | triangle angle relationships | step by step proof | theorem based proof | geometric reasoning | visual geometry proof | proof without calculus | triangle decomposition | high school geometry | learn geometry | geometry tutorial | math intuition