My Points: 2
Total Posts Answered:2
Answer Details:
Feb 19, 2012 05:10 PM
let A +B = pi/4
tan(A+B)=1
or, tanA +tanB = 1-tanAtanB
or, (1+tanA)(1+tanB)=2
use this result to obtain A+4A = pi/4
A= pi/20
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My Points: 88
Total Posts Answered:68
Answer Details:
Feb 19, 2012 05:27 PM
(1+tanA)(1+tan4A)=2,
1+tanA+tan4A+tanAtan4A=2,
tanA+tan4A+tanAtan4A=1,
tanA+tan4A=1-tanAtan4A,
(tanA+tan4A)/(1-tanAtan4A)=1,
tan(A+4A)=tan45,
tan5A=tan45,
thus 5A=45,
A=9.
then (a) is the ans.
The answer was approved by user!!!
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