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`        The value of  tan(pi/12) + 2tan(2 pi/12) + 4tan(4 pi/12) + 8cot(8 pi/12) ,is.   Ans: cot (pi /12) `
10 months ago

Arun
22281 Points
```							Dear student I want you to remember this- tan A + 2 tan 2A + 4 tan4A + 8cot 8A = cot A Hence for the above question, A = pi/12 Hence answer will be cot pi/12
```
10 months ago
Heisenberg
12 Points
```							But sir can you prove that part where you said that the result is important?remembering so many formulae plus so many results is a had job......
```
10 months ago
Arun
22281 Points
```							Dear student I am giving you some hint you can solve this then, take 8 cot 8A now open this in the form of tan 4A  after this you will clearly find ome common in terms one by one from right to left. and final result will be cot A
```
10 months ago
1646 Points
```							heisenberg an even better way to solve is to use the identity tanx= cotx – 2cot2xnote that the rth term of summation is 2^(r-1)tan(2^(r-1)y) where y is pi/12.write it as 2^(r-1)[cot(2^(r-1)y) – 2cot2^ry]= 2^(r-1)cot(2^(r-1)y) – 2^rcot2^ry, which is easily seen to telescope!
```
10 months ago
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### Course Features

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### Course Features

• 31 Video Lectures
• Revision Notes
• Test paper with Video Solution
• Mind Map
• Study Planner
• NCERT Solutions
• Discussion Forum
• Previous Year Exam Questions