Prove the following: if, in a triangle
ABC, angle BAO = angle OAC = 20°, angle ACO = 10°,and angle
OCB = 30°, then angle
OBC = 80°. Try to use elementary geometry (Euclid's Elements.)
See
also: Art 00
PicSketch  Pencil Sketch & Drawing Photo Filter Effects
PicSketch by Softease Tech Co., Limited is a photo sketch app
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