How do i Do this? Would I use law of sin or Cos?
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Question

How do i Do this? Would I use law of sin or Cos?
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anonymous · Answer

@jim_thompson5910

accessdenied · Answer

What are we trying to find here in particular?  All of the variables?
And if so, is there one in particular you were having trouble with?

anonymous · Answer

yes the abc and degress

accessdenied · Answer

|dw:1399255423544:dw|
Redrawing it here to make it easier to refer to..
The first thing I am seeing we could do here is finding the variable y.  If we are deciding between Law of Cosines and Law of Sines, we need to consider what information we have and what we want to find.
   Law of Sines:   sin A / a = sin B / b       Two Angles,  Two corresponding Sides
   Law of Cosines:   c^2 = a^2 + b^2 - 2 ab cos C      Three Sides, One Angle.

So to find y, we have two of the three sides, and we have one angle.  We just need one more side, y.  So Law of Cosines would work here!

accessdenied · Answer

Law of Sines would work to find another angle, but we have to find one unknown at a time.  To find y, we can't use Law of Sines yet because we only have one angle that is known -- 30 degrees.  So either we can use Law of Cosines and find y, or we might have to look for some other information to find the angle opposite of y.  Then apply Law of Sines.

anonymous · Answer

so C^2=6^2+ whats b? there is no number there

accessdenied · Answer

I'll explain both ways to give you an idea.

Law of Cosines:  We use the sides:  10, 6, and y.  The angle:  30 degrees, which is opposite the side length of 6.  Thus we can set up the equation:
     6^2 = y^2 + 10^2 - 2*y*10 cos (30 degrees).
Law of Sines:  We need to find an angle first.  We could find the angle W because we know angle 30 and opposite side 6.  We know the side length opposite W is 10.  So:
    sin 30 / 6 = sin W / 10
Once we solve for W here, we will know two of three angles of the triangle.  So the third angle is just 180 - the other two angles.  Then Law of Sines is applicable to find y!

anonymous · Answer

im so confused, so what i did up there correct>

accessdenied · Answer

c^2 = a^2 + b^2 - 2ab cos C
c is the side length opposite of the angle we know, 30 degrees.
a and b are the other two side lengths of the triangle.
|dw:1399256632163:dw|

You asked what b would be.  a=10,  b=y,  and c=6.  C=30 degrees.  Can you see where this is coming from?

anonymous · Answer

yeh

anonymous · Answer

so how things am i missing to find the info?

accessdenied · Answer

Sorry, I gotta go right now!
You should bump the question and try to get others to help for now.  Again, sorry for an abrupt leave.  :(

anonymous · Answer

Thnks for your help