Calculating the Exact Value of tan(15)

AI Thread Summary
The discussion focuses on calculating the exact value of tan(15) using the angle subtraction formula. The initial approach mistakenly uses 40 - 30 instead of the correct 45 - 30 to derive the equation. Participants clarify that the expression (1-√(3)/3)/(1 + 1 * √(3)/3) is on the right track for rationalizing the denominator. The conversation emphasizes the importance of correctly identifying the angles involved in the calculation. Ultimately, the correct formulation is essential for accurately determining tan(15).
big billy
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I am trying to find the exact value for tan(15). I figure my equation as 40 - 30 to give the 15.

when deriving my equation is where I have the problem. can anyone help please.

(1-√(3)/3)/(1 + 1 * √(3)/3)
 
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Looks good so far. To rationalize the denominator, multiply the top and bottom by (1-√(3)/3).
 
big billy said:
I am trying to find the exact value for tan(15). I figure my equation as 40 - 30 to give the 15.

when deriving my equation is where I have the problem. can anyone help please.

(1-√(3)/3)/(1 + 1 * √(3)/3)

40-30 \neq 15
:redface:
I think you mean 45-30
:smile:
 
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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