Angles on a straight line

In Diagram 1, ADC is a straight line.

Move B.

What do you notice about the sum of the two angles ADB and DBC?

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You should have discovered that the angles that make up a straight line add up to 180°. This is true in general.

In Diagram 2, angle FHG is marked as 60° and EHG is also a straight line.
So, angle FHE can be calculated as 180°-60°=120°.

Move the point F to get a new angle.
Calculate the angle FHG.

You can check your answer by selecting the 'Angle' tool.
Then left-click on the points F, H and G.
The value of the angle will be shown.
Move the value if needed so that you can read it clearly.

Note that the points should be selected in an anti-clockwise order.

For further practice, either use the reset button or delete the label and start again.

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