Posted by **Mike** on Thursday, April 5, 2012 at 11:42pm.

Find the indicated angle è.

(Use either the Law of Sines or the Law of Cosines, as appropriate. Assume a = 110 and c = 136 (angle B=38)

Round your answer to two decimal places.)

- Pre-Calc Helppp!!! -
**Henry**, Saturday, April 7, 2012 at 11:13pm
Law of Cosines:

cosB = (a^2+c^2-b^2)/2ac.

cos38 = ((110)^2+(136)^2-b^2) / 29920.

0.7880 = (30596-b^2) / 29920.

Cross multiply:

30,596-b^2 = 0.7880*29920 = 23576.96.

-b^2 = 23,976.96-30596 = -6619.04.

b^2 = 6619.04.

b = 81.36.

Law of Sines:

sinA/a = sinB/b.

sinA / 110 = sin38 / 81.36.

Multiply both sides by 110:

sinA = 110(sin38 / 81.36) = 0.832384.

A = 56.34 Deg.

C = 180 - 38 - 56.34 = 85.66 Deg.

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