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MathGroup Archive 1999

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Re: Solve and Trig functions

  • To: mathgroup at
  • Subject: [mg19334] Re: [mg19295] Solve and Trig functions
  • From: BobHanlon at
  • Date: Mon, 16 Aug 1999 02:15:00 -0400
  • Sender: owner-wri-mathgroup at


I assume that the intent is not to tell Mathematica the definition of Tan 
since it already knows the definition. Rather, the intent is to force it to 
use that knowledge. Consequently, I suggest you define the concept of 
dividing two equations as follows:

Equal /: Equal[a_, b_]/Equal[c_, d_] := Equal[a/c, b/d];

eq1 = a1 + b1 == Sin[fi];
eq2 = a2 + b2 == Cos[fi];

eq1/eq2 // Reverse

Tan[fi] == (a1 + b1)/(a2 + b2)

Bob Hanlon

In a message dated 8/14/99 5:45:38 AM, kevin.mccann at writes:

>If I have the following two equations:
>eq1 = a1 + b1 == Sin[fi];
>eq2 = a2 + b2 == Cos[fi];
>It is clear that
>Tan[fi] == (a1+b1)/(a2+b2)
>but how do I get Mathematica to recoginize this? This problem is trivial,
>with more complicated expressions, the answer may not be immediately 

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