Help with trigonometric equation tan(x)+cot(2x)=1 It is clear that the equation has a solution x=pi/4 but I can't show that this is the only solution. Any ideas?

Demarion Ortega

Demarion Ortega

Answered question

2022-11-16

Help with trigonometric equation tan ( x ) + cot ( 2 x ) = 1
It is clear that the equation has a solution x = π / 4 but I can't show that this is the only solution. Any ideas?
P.S. I am trying to solve the equation without using formulas for 2 a angle

Answer & Explanation

Ryan Davies

Ryan Davies

Beginner2022-11-17Added 18 answers

Actually, you don't have to use double angle formulas at all...
tan ( x ) + cot 2 x = 1 sin x cos x + cos 2 x sin 2 x = 1 sin x sin 2 x + cos x cos 2 x cos x sin 2 x = 1
A couple of hints:
1. What trick can you use to simplify sin x sin 2 x + cos x cos 2 x ?
2. Are there any extraneous roots? ( π 4 is correct; the general solution would be π 4 ± π k.)

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