Are lines AB and DC parallel?
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Are lines AB and DC parallel?
For the lines to be parallel, the two angles must be equal (according to the definition of corresponding angles).
Let's compare the angles:
Once we have worked out the variable, we substitute it into both expressions to work out how much each angle is worth.
First, substitute it into the first angle:
Then into the other one:
We find that the angles are equal and, therefore, the lines are parallel.
Yes
Identify the angle shown in the figure below?
Look for corresponding angles - they're in the same relative position when a transversal crosses two lines. In this problem, both angles are on the same side of the transversal and in matching positions.
If the angles aren't equal, then the lines are not parallel! Parallel lines always create equal corresponding angles, so unequal angles mean the lines intersect somewhere.
Yes! You must find the value of x by setting the expressions equal, then substitute back to find the actual angle measures. This proves whether they're truly equal.
Never estimate! Diagrams aren't drawn to scale. You must solve algebraically to get the exact angle measures. In this case, both angles equal exactly 50°.
Besides corresponding angles, you can also use:
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