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Inside scale from 0 o to 180 o going in an anti-clockwise direction. Outside scale from 0 o to 180 o going in a clockwise direction. A 180 o Protractor. You need to be able to measure an angle to the nearest degree. To help you do this you should always:.
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Inside scale from 0o to 180o going in an anti-clockwise direction. Outside scale from 0o to 180o going in a clockwise direction. A 180o Protractor
You need to be able to measure an angle to the nearest degree. To help you do this you should always: 1. Look directly down onto the cross point. (this avoids parallax errors) 2. Always use the protractor in a horizontal manner as shown below.
1 0 on the inside so use inside scale 2 0 on the outside so use outside scale Measuring Angles with a 180o Protractor 50o 67o
3 4 0 on the inside so use inside scale 0 on the outside so use outside scale Measuring Angles with a 180o Protractor 120o 135o
What’s in the box ? 0 on the inside so use inside scale 0 on the outside so use outside scale 1 Measuring Angles with a 180o Protractor 80o 2 55o
0 on the inside so use inside scale 0 on the outside so use outside scale 3 Measuring Angles with a 180o Protractor 150o 4 165o
Measure each angle in the shapes below. Answer on your worksheet. 2 3 1 6 5 4
Measure each angle in the shapes below. 900 2 3 1 670 670 680 900 900 1120 680 900 460 1120 6 5 4 480 1180 730 1070 900 1010 1010 420 1100 1100 1070 730 Rectangle 3600 Trapezium 3600 Triangle 1800 Parallelogram 3600 Triangle 1800 Pentagon 5400
1 2 4 3 6 5 Estimating Angles
D E F Naming Angles Angles are named using the three letters that form them. The middle of the three letters is the vertex of the angle (pointy bit) DEF or DÊFor FED or FÊ D
B A O Measuring Angles AOB = 27o AOC = 122° C A
Obtuse angle (between 90°and 180°) Right Angle (90°) Acute angle (less than 90°) Straight angle (180°) Reflex angle (more than 180°) Types of angle
What’s in the box 2 ? ACB or BCA 1 A * B C D P * R Q S What is the name of the angle marked with *? What type of angle is this? OBTUSE What is the name of the angle marked with *? 2 PQS or SQP What type of angle is this? ACUTE
x 130° O C Complementary angles add up to 90° So the complement of 40° is 50° 1 0 S Supplementary angles add up to 180° The supplement of 40° is 140° Angle Reasons x = 50° Adjacent angles on a straight line sum to 180°
70° x x 120° 80° 110° x = 70° Vertically opposite angles are equal x = 50° Angles at a point sum to 360°
x 50° x x 70° 50° x = 60° Angles in a triangle sum to 180° x = 50° Base angles of an isosceles triangle are equal x = 60° Each angle in an equilateral triangle is 60°
110° x transversal 110° x 50° x Angles on Parallel Lines x = 110° Corresponding angles on parallel lines are equal x = 50° Alternate angles on parallel lines are equal x = 70° Co-interior angles on parallel lines sum to 180° EXTENSION
Types of Triangles (according to sides) Scalene - no equal sides Isosceles - 2 equal sides Equilateral - 3 equal sides Types of Triangles (according to angles) Acute angled triangle - all angles equal Right angled triangle - one 90° angle Obtuse angled triangle - one angle 90°
What’s in the box 3 ? co 125o ao 100o bo 35o a = 55 b = 125 To find c you must use the new fact that in all triangles the three angles add up to 180o c = 65