The circumference of the circle is found using the formula C = 2 PI r
Circumference = 2 *PI * 15.5 = 31pi
The angle is 90 degrees, which is 1/4 of a complete circle ( 360 degrees).
The arc length would be 1/4 of the circumference:
Arc length = 31pi / 4 = 7.75PI
If arc =AB is equal to arcCD then line AB should equa lineCD
<u>Answer-</u>
<em>The correct answer is</em>
<em>∠BDC and ∠AED are right angles</em>
<u>Solution-</u>
In the ΔCEA and ΔCDB,

As this common to both of the triangle.
If ∠BDC and ∠AED are right angles, then 
Now as
∠BCD = ∠ACE and ∠BDC = ∠AED,
∠DBC and ∠EAC will be same. (as sum of 3 angles in a triangle is 180°)
Then, ΔCEA ≈ ΔCDB
Therefore, additional information can be used to prove ΔCEA ≈ ΔCDB is ∠BDC and ∠AED are right angles.
First part, in quadrilateral WXYZ, WX is parallel to ZY because both sides are equal while the other parallel segments WZ and XY are equal but different side lengths.
The measure of angle Z is 78 because both of the pictures are the same, only rotated. and angle S and Z are acute.