Find the size of the angles marked with a letter on the triangle pose shown. Write down the axiom or theorem used in each case.
36°
5. The following is a sketch of a type of roof called a fi nk. Some angles are marked in the diagram.
Note also that |AD| = |AE| Find the following angles. (i)
(ii)
|∠BDC| |∠ADC|
B H 75° Y G
4. The diagram below is of a triangular house. |∠BAC| = 32 ° and |AB| = |AC|
Find the following angles and the type of triangle. (i)
(ii)
|∠ACB| |∠CBA|
(iii) |∠DBA|
(iv) What type of triangle is ∆ ABC ?
A C A
50°60° 45°
D 45°
50° E
6. A triangular fi eld has the shape of an equilateral triangle. The real-life size of one of the sides of the equilateral triangle is 1·5 km. Using an appropriate scale, draw a scale diagram of this fi eld.
7. The diagram below is used as part of the proof of the theorem which states that each exterior angle of a triangle is equal to the sum of the interior opposite angles.
(i) What is the total value for the sum of the angles |∠M| and |∠N| ? Give a reason for your answer.
(ii) What is the total value for the sum of angles |∠P| , |∠O| and |∠N| ? Give a reason for your answer.
C D B C P B O
N M A
8. Copy the table below and put a tick (✓) in the correct box in each row to show whether each statement is always true, sometimes true, or never true, for any triangle.
Statement
(i) Each exterior angle in a triangle is equal to the sum of the two opposite interior angles.
(ii) The included side is the side between two angles in a triangle.
(iii) It is possible to construct a triangle when we only know one angle and one side.
(iv) The sum of three angles in a triangle is equal to 180 °. (v) A triangle can contain two 90° angles.