# Angles

## 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°

## Compass Bearing

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°