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T_T
Lv 4
T_T asked in Science & MathematicsMathematics · 9 years ago

Prove cos^2(x)=1/(1+tan^2(x)) only by manipulating the LHS?

It's pretty easy to prove the equation by changing the right hand side but I want to know how to approach the question if it is only the left hand side which can be altered.

Update:

I need to be able to show that I can go from one line involving cos^2(x) to another line involving 1/(1+tan^2(x)) in a certain question.

Also, 1/sec^2(x)=1/(1+tan^2(x)) is kind of cheating since it relies on knowledge that the RHS can be converted to the LHS but not being able to show the other way around.

Update 2:

Figured it out.

LHS = cos^2(x)

LHS(cos^2(x) + sin^2(x)) = cos^2(x)

LHS(cos^2(x)/cos^2(x) + sin^2(x)/cos^2(x)) = 1

LHS(1 + tan^2(x)) = 1

LHS = 1/(1+tan^2(x))

LHS = RHS

1 Answer

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  • 9 years ago
    Favorite Answer

    Looks like you already done it :)

    Nice work

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