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Home Q & A Board Science-Related Homework Help Mathematics
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lfiorill lfiorill
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11 years ago
you have a Triangle, top angle is 75 degrees, left bottom angle is 40 degrees. bottom line (base) is 4cm left side is what you are looking for, you don't have bottom right angle or right side.
pleas help.
thanks.
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toms.girltoms.girl
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11 years ago
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#2
11 years ago
There are 180 degrees inside a triangle.  

So the bottom right angle = 180 - 75 - 40 = 65 degrees

Law of Sines

a / sin A  = b / sin B = c /sin C  

It is understood that side a is opposite angle A, side b is opposite angle B, and side c is opposite angle C.

We want the side opposite the 65 degree angle.

so....

X / sin 65  = 4 / sin 75

Therefore, X = (4*sin 65) / sin 75  = 3.753 cm
wrote...
#3
11 years ago
you have the angle for the first 2. just add it up and subtract it by 180, so u will get the right bottom angle. then u can do it now to find all the sides. by sinC/c=sinA/a which is sin75/4=sin40/a. a=2.7 then do it with the small b.
lfh
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#4
11 years ago
OK  first, figure out what the angle is across from the unknown side you want to figure out.  You have the other two angles, so the missing angle is:
180 - 75 - 40= 65 deg.

the angle right across from the side you do know is 75 deg.  So now using the law of sines you know that this ratio:  4 cm/sin 75deg  = this ratio : x cm/ sin65 deg

You got it from there?
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