Which of the following gives the length of chord DF in the figure above ?

A) 2cos(1.7)
B) 2sin(1.7)
C) 4cos(0.85)
D) 4sin(0.85)

Leave the figure in the comments.

Comments (3)

You’ll want to use radian angle measures here. Since the radius of the circle is 2, its circumference is 4π. Angle DCF will be (3.4)/(4π) * 2π radians = 1.7 radians. That means angles DCE and FCE each measure 0.85 radians.

From there, just look at one of the triangles (and remember to double what you find at the end). I’ll look at the bottom triangle.

sin(0.85) = EF/2
2 sin(0.85) = EF

So half the chord is 2 sin(0.85). That means the full chord will be 4 sin(0.85)

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