Respuesta :

wolf1728

We need to use the Law of Cosines:

cos (C) = (a^2 + b^2 -c^2) / 2 ab

cos (C) = (22^2 + 20^2 -18^2) / (2 * 22 * 20)

cos (C) = (484 + 400 - 324) / (880)

cos (C) = 560 / 880

cos (C) = 0.6363636364

arc cosine (C) = 50.479 Degrees


Source

1728.com/trigtut2.htm

(Scroll down to All 3 sides of a triangle)



Ver imagen wolf1728
Ver imagen wolf1728
jcherry99

Remark.

My favorite. The Cos Law. Straight forward. Just use it once and it gives just one reply.


You want the angle opposite 18 feet. C is the one.


Formula

c^2 = a ^2 + b^2 - 2*a*b*Cos(C)


Givens

a = 22

b = 20

c = 18


Sub and solve

18^2 = 20^2 + 22^2 - 2*20*22*Cos(C)

18^2 = 400 + 484 - 880 * Cos(C)

324 = 400 + 484 - 880 * Cos(C)

324 = 884 - 880 * Cos(C)

-560 = - 880 * Cos(C)

-560/-880 = Cos(C)

0.6364 = Cos(C)


Now we have to go through that weird inverse thing.

2nd F

cos^-1

(0.6364

)

=

C = 50.48 degrees.




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