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WARM UP

WARM UP. Measuring, calculating and drawing angles. Our learning objectives today To use a protractor to: measure acute and obtuse angles to the nearest degree. draw acute and obtuse angles to the nearest degree. To calculate angles on a straight line.

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WARM UP

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  1. WARM UP

  2. Measuring, calculating and drawing angles... Our learning objectives today To use a protractor to: • measure acute and obtuse angles to the nearest degree. • draw acute and obtuse angles to the nearest degree. To calculate angles on a straight line. Powerpoint hosted on www.worldofteaching.com Please visit for 100’s more free powerpoints

  3. Name the angles in the figure: SOLUTION: There are three different angles. PQS or SQP SQR or RQS PQR or RQP Ex.1: Naming Angles You should not name any of these angles as Q because all three angles have Q as their vertex. The name Q would not distinguish one angle from the others.

  4. Note: • The measure of A is denoted by mA. The measure of an angle can be approximated using a protractor, using units called degrees(°). For instance, BAC has a measure of 50°, which can be written as mBAC = 50°. B A C

  5. Angles that have the same measure are called congruent angles. For instance, BAC and DEF each have a measure of 50°, so they are congruent. more . . . 50°

  6. Classifying Angles • Angles are classified as acute, right, obtuse, and straight, according to their measures. Angles have measures greater than 0° and less than or equal to 180°.

  7. What do we use to help us? A protractor Here is a standard protractor like you use in the classroom.

  8. When we use a protractor, we need to line it up correctly. You need to make sure the protractor is lined up correctly. Is this ready to measure the angle?

  9. Were you right......................it wasn’t Look for the upside down ‘T’ in the middle of the straight line on your protractor. This needs to be exactly on the vertex of your angle.

  10. We need to remember..... It doesn’t matter which way round the angle is, you ALWAYS need to line the upside down ‘T’ to the vertex of the angle.

  11. Now you are ready. Read from the 0°, and follow the inner set of numbers.

  12. Once you reach 30° you need to be careful!!! You then need to look at the 1° markings on the outer set of numbers.

  13. What does it measure? This angle measures 35°.

  14. Measuring, calculating and drawing angles... Remember our learning objectives today are To use a protractor to: • measure acute and obtuse angles to the nearest degree. • draw acute and obtuse angles to the nearest degree. To calculate angles on a straight line.

  15. Classifying Angles • Angles are classified as acute, right, obtuse, and straight, according to their measures. Angles have measures greater than 0° and less than or equal to 180°.

  16. Closure Question: • Describe how angles are classified. Angles are classified according to their measure. Those measuring less than 90° are acute. Those measuring 90° are right. Those measuring between 90° and 180° are obtuse, and those measuring exactly 180° are straight angles.

  17. Classifying Angles • Angles are classified as acute, right, obtuse, and straight, according to their measures. Angles have measures greater than 0° and less than or equal to 180°.

  18. Ex. 3: Classifying Angles in a Coordinate Plane • Plot the points L(-4,2), M(-1,-1), N(2,2), Q(4,-1), and P(2,-4). Then measure and classify the following angles as acute, right, obtuse, or straight. • LMN • LMP • NMQ • LMQ

  19. Ex. 4: Drawing Adjacent Angles • Use a protractor to draw two adjacent acute angles RSP and PST so that RST is (a) acute and (b) obtuse.

  20. Ex. 4: Drawing Adjacent Angles • Use a protractor to draw two adjacent acute angles RSP and PST so that RST is (a) acute and (b) obtuse. Solution:

  21. Closure Question: • Describe how angles are classified. Angles are classified according to their measure. Those measuring less than 90° are acute. Those measuring 90° are right. Those measuring between 90° and 180° are obtuse, and those measuring exactly 180° are straight angles.

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