Third Year Drawing by D. R. Augsburg Third Year Drawing by D. R. Augsburg    

Lesson 2: Acute, Right, and Obtuse Triangles (Form)

lesson image

The instructor tells children:

  • Form tells about the shape of objects.
  • The simplest forms are triangles, rectangles, circles, ellipses, and ovals.
  • These forms in mathematics are called geometrical forms, and in drawing, measures of form.
  • These measures of form are common in animals and birds.
  • When it comes to the triangle, "tri" means three and "triangle" means three angles.
  • Thus, a triangle is a figure with three angles.
  • To call out the general shape of each animal in the top picture.

The instructor:

  • Asks children to study the image labeled "Angles and Triangles."
  • Tells children that right means straight, acute means sharp, and obtuse means dull.
  • Uses their forefinger to make right angles, acute angles, and obtuse angles and asks children to name each one as they are made.
  • Asks children to find these angles in their surroundings.
  • Draws the three kinds of angles in various ways and asks children to name them.

Children complete the following drill work:

  1. Draw a right angle.
  2. Draw an acute angle.
  3. Draw an obtuse angle.

Children study the below image and complete the following drill work:

  1. Draw the right triangle A.
  2. Draw the right triangle C.
  3. Draw the right triangle D.
  4. Draw the right triangle F.
  5. Draw the acute triangle B.
  6. Draw the acute triangle E.
  7. Draw the obtuse triangle G.
  8. Draw the obtuse triangle H.