The blue unit circle has a diameter and several colored chords. The red chord bisects the angle between the green chords. Express the sum of the green chords in terms of the red and purple chords.
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Solution
Green=red*purple.
Apply Ptolemy’s theorem to DFBE: g1*BE+g2*BF=r*FE g1+g2=r*FE / BE=r*2*GE/BE=r*2*b/2=r*b.