Question

Find the measure of b

Answer 1

Answer:  100

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Explanation:

Let's add angle c to the diagram such that it's adjacent to angle b, and inside the quadrilateral. Notice how angle c is opposite the 100 degree angle of this inscribed quadrilateral.

For any inscribed quadrilateral, the opposite angles are supplementary

c+100 = 180

c = 180-100

c = 80

Angles b and c are supplementary as well, because they form a straight line.

b+c = 180

b+80 = 180

b = 180-80

b = 100

In short, angle b is the same measure as that 100 degree angle in the diagram.

Answer 2

Step-by-step explanation:

Hi there!

From the above figure;

Let "x" be an unknown angle.

Then;

100° + X = 180°. { The opposite angles of cyclic quadrilateral is supplementary}

X = 180°-100°

Therefore, X= 80°.

Now;

X+b = 180°. {linear pair}

80° + b = 180°

Therefore, b = 100°.

[Next method:

b = 100° {When any side of cyclicquadrilateral is extended the external angle is equal to opposite interior angle.]

Hope it helps.