SOLUTION: In triangle ABC, angle A=120 and angle B is twice angle C. Find angle B and angle C.

Algebra ->  Triangles -> SOLUTION: In triangle ABC, angle A=120 and angle B is twice angle C. Find angle B and angle C.      Log On


   

Question 940766: In triangle ABC, angle A=120 and angle B is twice angle C. Find angle B and angle C.
Answer by macston(5194) About Me  (Show Source):
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A + B + C = 180 The sum of angles in a triangle is 180 degrees
A=120; B=2C
120+B+C=180 Subtract 120 from each side
120+B+C-120=180-120
B+C=60
2C+C=60 Substitute for B
3C=60
3C%2F3=60%2F3 divide both sides by 3
C=20 ANSWER 1 Angle C=20 degrees
A+B+C=180
120+B+20=180
B+140=180
B+140-140=180-140 Subtract 140 from both sides
B=40 ANSWER 2 Angle B=40 degrees
CHECK:
B=2C
40=2(20)
40=40