Measuring Angles with a Protractor
- Before measuring, estimate how many degrees the angle is.
- Place the cross-hairs of the protractor at the vertex of the angle (the point where the two lines meet).
- Place the base line of the protractor on one of the lines making the angle.
- Follow the second line and choose which of the outer rings has the correct number of degrees.
- To measure angles greater than 180 degrees, it is easier to measure the smaller angle and subtract from 360.
Types of Angles
|DIAGRAM||NAME OF ANGLE||SIZE OF ANGLE|
|Acute angle||Less than 90°|
|Right angle||Equal to 90°|
|Obtuse angle||Between 90° and 180°|
|Straight angle||Equal to 180°|
|Reflex angle||Between 180° and 360°|
Cardinal Points - Directions in words e.g. north, south, east, west, north-east, south-east
Compass Bearings - Directions in numbers of degrees that are measured clockwise from north as follows:
- North - 0°
- North-east - 45°
- East - 90°
- South-east - 135°
- South - 180°
- South-west - 225°
- West - 270°
- North-west - 315°
Question - Orienteering
Orienteering is a sport that uses navigational skills of reading maps and compasses while running through mountains and valleys. If I leave home and I travel the following legs of my journey, how far and at what bearing from home will I be? (In your sketch, use a scale of 1 cm for each 1 km.)
- 2 km at 0°
- 3 km at 90°
- 4 km at 180°
- 3.6 km at 236°
Did You Know That...?
Mandalas are complex geometric designs for quiet contemplation in the Buddhist and Hindu religions.