16. Draw rectangle KLMN. Bisect the sides of the rectangle and mark the points A, B, C and D. Join the points as a quadrangle. Find the perimeter of the quadrangle.

17. Through the given point one can draw .......................perpendicular lines to this straight line.

18. Draw line v and mark point T outside the line. Recall how to draw a perpendicular line to the given line through point T. Do it.

19. Draw a right angle and mark point B between its legs. With the help of compasses draw cross-section to the legs from point B.

20. Draw triangle ABC and a cross-section from point B to side AC. Measure the distance between vertex B and side AC.

21. Draw an angle of 80°. Mark point S on the leg of the angle. Find the distance of the point from the other leg of the triangle.