How do you find all three angles ?Are there any proof of how to claim all three?

asked 7 years ago

Larrousse gravatar image

For a triangle of ABC the sides of a,b,c are written in a way of a=sinAsinC, b=sinBsinC, c=sinCsinC and the heights ha,hb,hc are written in a form hcha=,hchb=,hchc to give us a and b. and the base c=1.

If I have a triangle with sides 5,5,4 and their altitudes are 21,13.44,13.44 , why do they simplify to give us a special kind of triangle where a=1.25,b=1.25,c=1

2113.44=1.25

Angles 3=0.16+0.16+0.682+0.84+0.84+(10.682)

Laws of Cosine ,when we have all 3 lengths are:

a2=b2+c22bccos(A)

b2=a2+c22accos(B)

c2=a2+b22abcos(C)

Here we have sides 1.25,1.25and1,a simplest version of the triangle measuring 5,5,4.

And for three sides of a triangle a,b,c,and ABC. The legs of the heights ha,hb,hc are situated on three sides of the triangle. For one side a I have bcos(A)cos(C)=a and for the second side b I have acos(B)cos(C)=b and the third side which is c as the base of the triangle equals to 1.

sin2(B)+(acos(B))2=b

sin2(A)+(bcos(A))2=a

sin2(A)+(cos(A))2=c

by using consecutive or non consecutive numbers: a<b<c="" we're="" able="" to="" define="" θ="" without="" conversion="" <="" p="">

ac=cos(C) (1ac)×(a+c)(ca)=sin(C)

(cb)c=cos(B) bc=sin(B)

Find

cos(A) & sin(A) which we already know.

Question is: why hchb; hcha;hchc and. sinAsinC; sinBsinC sinCsinCequal to the sides a,b,c?

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Comments

This is not the right place, this site is supporting the computer algebra system named Sage and/or SageMath. However, since the answer to the only question can be quickly given...

Above: sinC/sinC is obviously 1, which is not always equal to c. So the question claims a false statement. What is on the path of the truth is as follows:

Let R be the side of the circumscribed circle. Then a=2RsinA and the other relations, so we get the "sine law" a/sinA=b/sinB=c/sinC=2R.

The other claim is also false, but something can be simply traced back from 2S=aha=bhb=chc, where S is the surface of ΔABC.

So the proportion a:b:c corresponds to (1/ha);(1/hb):(1/hc).

dan_fulea gravatar imagedan_fulea ( 7 years ago )

Please take a look at the sagemath tour .

For instance, let A,B,C be the angles in a triangle. Then we may ask sage for the following...

sage: var( 'A,B,C' );
sage: E = 4*sin(A)*sin(B)*sin(C)
sage: E.reduce_trig()
-sin(A + B + C) + sin(A - B + C) + sin(-A + B + C) - sin(-A - B + C)

Now, the term sin(A+B+C)=sin180 vanishes. And for the other terms, we may write simpler expressions, e.g. sin(A+B+C)=sin((A+B+C)2A=sin(1802A)=sin(2A) .

We can check the equality:

sage: var( 'A,B' );
sage: C = pi-A-B
sage: bool( ( 4*sin(A)*sin(B)*sin(C) == sin(2*A)+sin(2*B)+sin(2*C) ).reduce_trig() )
True
dan_fulea gravatar imagedan_fulea ( 7 years ago )