Recall that:
Vertically opposite angles are the angles that are opposite to
each other, and these angles are equal.
Example 5
Use the information given in the diagram to find x and y. Give reasons
for your answers.
Solution:
Angles Forming a Circle
Recall that:
The sum of all angles that meet at a point is equal to
360º.
There are 360º in one complete revolution. So, the sum of the angles
with a common vertex is equal to 360º.
In the diagram, angles a, b, c and d form a
circle with a common vertex. So:
a + b + c + d = 360º
Example 6
Use the information given in the diagram to find x. Give reasons
for your answer.
Solution:
So, the value of x is 205.
Key Terms
vertically opposite angles, angles
forming a circle
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