The angle at the circumference in a semi-circle is 90°. Angle STU = 90° Angles in a triangle add up to 180°. The angle on a straight line is 180°. The angle VOY = 180°. The angle at the ...

If such an obstacle as the horizon does not shut the view completely and the observer catches the sun and water droplets at the appropriate angle relative to his position, then the whole circle of ...