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Mathematics 7 Online
OpenStudy (anonymous):

math hw

OpenStudy (ranga):

Are you going to post the question?

OpenStudy (ranga):

Use the Law of Cosines to find the angles. c^2 = a^2 + b^2 - 2abcos(C) where C in cos(C) is the angle included between sides a and b.

OpenStudy (ranga):

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OpenStudy (ranga):

No square root in this problem because we need to find the angle C (upper case) not the length of the side c (lower case).

OpenStudy (ranga):

Yes, but a calculator should be able to handle it.

OpenStudy (ranga):

c^2 = a^2 + b^2 - 2abcos(C) We need to solve for C. Isolate cos(C): 2abcos(C) = a^2 + b^2 - c^2 cos(C) = ( a^2 + b^2 - c^2 ) / (2ab) You have: c = 255; a = 270; b = 442.85. Find cos(C). Then take the inverse and find angle C.

OpenStudy (ranga):

I am getting cos(C) = 0.8530 C = inverse cosine of 0.8530 = 31.5 degrees. Use the law of cosines to find one more angle, either A or B. Then the third angle of the triangle can be found by using the fact that three angles of a triangle add up to 180 degrees.

OpenStudy (ranga):

a^2 = b^2 + c^2 - 2bccos(A) 2bccos(A) = (b^2 + c^2 - a^2) cos(A) = (b^2 + c^2 - a^2) / (2bc)

OpenStudy (ranga):

I am getting cos(A) = 0.8335 Take the inverse cosine to find angle A

OpenStudy (ranga):

Yes. A and B are correct.

OpenStudy (anonymous):

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