Splitting a trigonometric equation into cases I am not understanding this step in a solution I found. We are solving y=(-2y)/(1-y^2) where y=tan(x).

c0nman56

c0nman56

Answered question

2022-10-26

Splitting a trigonometric equation into cases
I am not understanding this step in a solution I found. We are solving
y = 2 y 1 y 2
where y = t a n ( x )
The solution says that we can now split this into two cases, case 1 where y = 0 and case 2 where y 0, I do not understand how we know that we can split up into two cases at this point, please advise. What's the motivation?
(As a side note, the cases are
case 1, y=0
x = k π , k Z
case 2, y 0
1 y 2 = 2 y 2 = 3
then
x = ± π 3 + k π , k Z ).

Answer & Explanation

Travis Sellers

Travis Sellers

Beginner2022-10-27Added 18 answers

One would be tempted to cancel out the term y from the numerators on both sides. i.e. write it as
1 y 2 = 2 y y = 2
. That would be valid only when y 0, since you would be dividing 0 by 0 when y = 0. Hence the motivation to treat y = 0 as a special case.

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