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how should we find the angle between the sides of a triangle if only the sides are given.
eg: AB=3 BC=4 CD =5.FIND ANGLE A B AND C in triangle ABC.
plss help

2006-10-05 03:08:26 · 5 answers · asked by theking 2 in Science & Mathematics Mathematics

also what if not a right triangle

2006-10-05 05:31:41 · update #1

5 answers

this is a right angled triaangle. the angle opposite side bc is therefore 90. now we have 90degrees left. since side AB is 3 therefore the angle opposite it will be 3/7of 90 or 3/12 of 180 taking the fraction of the sum of the sides. then do the same for the angle opposite side ca . you have by mistake included another point d .

2006-10-05 03:31:24 · answer #1 · answered by Anonymous · 0 0

Has your teacher taught you SOH, COH, TOA?

That is one way used to determine angles of a right triangle with known sides. It can also be used to determine the measurements of a triangle if you know only some of the sides and some of the angles.

First, you need to make sure it is a right triangle. From the Pythagoras Theorem, we know that a right triangle can be written in the form a^2+b^2=c^2. We have 9 + 16 = 25, so this is a right triangle.

For this, I'll designate ang as the angle you want to know (not the right angle, obviously), adj as the side adjacent to that angle, opp as the side opposite from that angle, and hyp as the hypotenuse.

SOH
Sin(ang) = opp/hyp
CAH
Cos(ang) = adj/hyp
TOA
Tan(ang) = opp/adj

So, looking at your triangle, we can see that AC=5 is the hypotenuse. We know this because the hypotenuse is the longest side and is opposite of the right angle. That right angle is angle B.

We know all three sides, so feel free to use any of SOH, CAH, TOA.
Sin(A) = opp/hyp = BC/AC = 4/5
Sin(C) = opp/hyp = AB/AC = 3/5

The inverse sine of 4/5 is roughly 53.1 degrees, while the inverse sine of 3/5 is roughly 36.9 degrees.

There are other ways, but since your example involves a right triangle, I went for the simpler method.

I'm not sure how far along you are in class, so I may have just thrown some material at you that your teacher isn't ready to present yet.

2006-10-05 10:11:00 · answer #2 · answered by Rev Kev 5 · 1 0

Draw a line segment AB=3
From B draw an arc of 4
From A draw an arc of 5
Both the arcs meet at a point. This is point C.
The triangle ABC is constructed.
Now find the angles using your Protractor.
In your question, you have mentioned CD=5.
It's not CD, it's CA=5.

2006-10-05 10:16:21 · answer #3 · answered by syam p 2 · 0 0

I will give u a hint" 3 angles of a triangle =180 degreesssss

2006-10-05 10:11:38 · answer #4 · answered by $/\/@ZZY G@L 3 · 0 1

Go with rev key and forget the rest

2006-10-05 10:28:36 · answer #5 · answered by curious george 5 · 0 0

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