Find exact value difference identity

AI Thread Summary
To find the exact value of Tan(3/4 - 12/5), the formula tan(x-y) = (tan(3/4) - tan(12/5)) / (1 + tan(3/4)tan(12/5) can be applied. The user expresses confusion about obtaining exact values for the tangent ratios and considers simply subtracting the angles to find tan(-33/20). There is a suggestion that the exact answer may actually be the negative tangent value obtained. The discussion highlights the challenge of calculating exact trigonometric values under pressure. Ultimately, the user reflects on possibly overcomplicating the problem.
synergix
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Homework Statement


Find the exact value of the expression Tan(3/4-12/5)

Homework Equations



tan(x-y)= (tan3/4 -tan12/5)/ (1+tan3/4tan12/5)

The Attempt at a Solution



I am not sure how to get exact values for these ratios. I haven't been able to get past this point
 
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synergix said:
Find the exact value of the expression Tan(3/4-12/5)

Hi synergix! :smile:

Why can't you just subtract 12/5 from 3/4, and then look up the tan? :confused:
 
I amnot sure what you mean by look up the tan. I get tan(-33/20) when I subtract them. I can get the answer just not the exact answer.
 
uhhhh... I guess that would be the exact answer... maybe I have confused myself haha.. I'm under a bit of pressure right now to get this done perhaps I have overcomplicated this
 
he he :biggrin:
 
I tried to combine those 2 formulas but it didn't work. I tried using another case where there are 2 red balls and 2 blue balls only so when combining the formula I got ##\frac{(4-1)!}{2!2!}=\frac{3}{2}## which does not make sense. Is there any formula to calculate cyclic permutation of identical objects or I have to do it by listing all the possibilities? Thanks
Since ##px^9+q## is the factor, then ##x^9=\frac{-q}{p}## will be one of the roots. Let ##f(x)=27x^{18}+bx^9+70##, then: $$27\left(\frac{-q}{p}\right)^2+b\left(\frac{-q}{p}\right)+70=0$$ $$b=27 \frac{q}{p}+70 \frac{p}{q}$$ $$b=\frac{27q^2+70p^2}{pq}$$ From this expression, it looks like there is no greatest value of ##b## because increasing the value of ##p## and ##q## will also increase the value of ##b##. How to find the greatest value of ##b##? Thanks
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