Being able to identify an angle can help us in this lesson. Let's try this problem to review.
Select the obtuse angle:
Let's learn more about angles on a straight line.
Find the size of the missing angle.
Angles on a straight line always add up to $180$180 degrees.
Investigate with and without digital technologies, angles on a straight line, angles at a point and vertically opposite angles. Use results to find unknown angles.