Find the soln...trigo series

(1 + tan5°) (1 + tan10°) (1 + tan15°).........( 1 + tan45°) = 2k ,

then k equals ___

then answer is an integer (0 - 9)

2 Answers

62
Lokesh Verma ·

Hint:

(1 + tan A°)(1 + tan (45°-A)) =

1
aditya ravichandran ·

\tan(A-B)=\frac{\tan{A}-\tan{B}}{1+\tan{A}\tan{B}}\\ \text{Put A=pi/4;B=x} \\ (1+\tan(\frac{\pi}{4}-x)-1)=\frac{1-\tan{x}}{1+\tan{x}}\\ \boxed{(1+\tan(\frac{\pi}{4}-x))(1+\tan{x})=2}\\ \text{so we can club the conjugates i.e 5,40;10,35;15,30;20;25}\\ \texttt{Answer:5}

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