Try some yourself
(a) How would you refer to angle α in this triangle by means of the letters A, B and C?
(b) Measure α with a protractor , if you have one, or otherwise estimate it.
(c) What type of angle is α?
(d) Find β without using a protractor using the fact that the three angles of a triangle always add up to 180°.
(a) Any of the following could be used: , , BAC, , CAB.
(b) α = 80°.
(c) Because α is less than 90°, it is an acute angle.
(d) As the three angles of a triangle always add up to 180°,
2 This pie chart shows the proportions of people voting for four parties in a local election.
(a) Measure the angles of the four slices of the pie with your protractor or estimate them if you don't have a protractor.
(b) Check your measurements by ensuring that the angles add up to 360°.
(c) Work out the percentage of the total vote polled by each of the four parties.
(a) Red party: 120°.
Blue party: 95°.
Yellow party: 95°.
Green party: 50°.
(b) 120° + 95° + 95° + 50° = 360°.
(c) Since 360° represents 100%, 1° will represent or .
So the Red party polled
The Blue party and the Yellow party polled
The Green party polled