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