
Doug C. answered 03/01/18
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Hi Bea,
Take a look at the following graph. I think it will give you the idea.
https://www.desmos.com/calculator/joydlmt3nv
Use Law of Sines on the green triangle to determine the hypotenuse of the red dotted triangle. Then use trig ratio "cosine" to find the distance to the building.

Doug C.
Hi Bea, Sorry I just saw your question. The "big" triangle is a right triangle. The acute angle in the upper left hand corner is 10 + 12 or 22. So the other acute angle is the complement of 22, i.e. 68.
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03/09/18
Bea L.
03/03/18