Denebel
How do I solve 8cos x = (sec x)^2?



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ksmith197
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sec^2x = 1/cos^2x

ksmith197
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8cos^3x=0

ksmith197
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cos(pi/2) = 0

ksmith197
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so 8cos^3(pi/2)=0

Denebel
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I got lost on the first step.. Sorry, can you explain it more?

ksmith197
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sure, first you need to memorize all of the identitites
memorize : sec(x) = 1/cos(x)

Jemurray3
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whoa whoa whoa,
\[8\cos^2(x) = 1\] not zero...

ksmith197
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so sec^2(x) = 1/cos^2(x)

ksmith197
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ah right 1 my bad

Denebel
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dw:1329118155688:dw So like this?

ksmith197
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anyway multiply across so 1/cos^2(x) * cos^2(x) = cos^2(x) * 8cos(x)

ksmith197
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1 = 8cos^3(x)

Denebel
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Ohh I see. Thank you.

Denebel
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So it would be x = pi/3 instead of pi/2 right?