9514 1404 393
Answer:
1. DE=104°, FE=76°, DEF=180°, CFD=284°, DFE=256°
6. x=6
7. DE=167°, EF=13°, DFG=347°
Explanation:
To solve these problems, you make use of the relationships between arcs and angles in a circle. Any resulting equations are solved in the usual way.
- the sum of arcs around a circle is 360°
- a diameter divides a circle into two 180° arcs
- vertical angles are congruent
- the measure of an angle is the sum of the measures of its parts
- the measure of an arc is the same as the measure of its central angle.
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1. A central angle of 104° is shown. The two diameters divide the circle into 4 arcs. Two will have measures of 104°, the other two will be supplementary to those, so will have measures of 76°. The blanks can be filled by adding the arcs necessary to achieve the arc measure asked for.
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6. Angles EFC and BFA are vertical angles, so have the same measure. Angle EFC is shown as being the sum of 90° and 27°. This means ...
90+27 = 21x -9 . . . . . . two-step linear equation in x
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7. The two marked arcs add to half a circle:
(x -3)° +(12x -25)° = 180° . . . . . . . two-step linear equation in x
Once you have the value of x, you need to substitute it into the formulas for each of the arc measures, then make use of any necessary sum-of-arc relations to find the necessary arc lengths.