#### Mathematics 3 ESO – Unit 11 PLANE GEOMETRY extra activities

**1 – ** Watch the video on “Polygons” and answer:

- a) What is a polygon?
- b) Why is the first figure not a polygon?
- c) Why is the second figure not a polygon?
- d) Why is the third figure not a polygon?
- e) Why is the fourth figure not a polygon?

**2 – ** Watch the video on “Types of triangles by sides and angles” and answer:

- a) What type of triangle has three different angle measures? Why does it have three different angle measures?
- b) What type of triangle has three equal sides? Why is its angle measure 60°?
- c) What is the minimum number of acute angles in a triangle?
- d) What determines the type of triangle (considering angles)?
- e) What is an obtuse triangle?
- f) What type of triangle has a 90° angle?

**3 – ** Watch the video on “Each Interior Angle of a Regular Polygon” and answer:

- a) What represents “n”?
- b) Use the formula to find the interior angle of:
- I) An equilateral triangle.
- II) A square.
- III) A regular pentagon.

**4 – ** Watch the video on “The Pythagorean Theorem” and answer:

- a) In the video, what letter represents the hypotenuse?
- b) In the video, what letters represent the legs?
- c) To what type of triangles does the Pythagorean Theorem apply?
- d) What symbol marks the right angle?
- e) What side is always opposite the right angle?
- f) What is the equation telling us?
- g) What means “relative” lengths?
- h) How can we check the Pythagorean Theorem with geometric squares?
- i) Calculate the length of the hypotenuse if the lengths of the legs are 5 cm and 2 cm.
- j) Calculate the length of one leg if the hypotenuse is 10 m and the other leg is 4 m.