How do you solve for Angles A, B, C if a=20 b=30 c=25?

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Answer 1 · 2018-03-20T06:27:18

#C~~55.77^@, B~~82.82^@, and, A~~41.41^@#.

By the cosine formula, we have,

#cosA=(b^2+c^2-a^2)/(2bc)#,

#=(30^2+25^2-20^2)/(2*30*25)#,

#=1125/1500#.

# rArr cosA=0.75#.

#:. A=arc cos 0.75~~41.41^@#.

#B=arc cos ((c^2+a^2-b^2)/(2ca))#,

#=arc cos((625+400-900)/(2*25*20))#

#=arc cos(0.125)#.

# :. B~~82.82#.

Finally, #C~~180^@-(41.41^@+82.82^2)=55.77^@#.