Question 204698
verify that each of the following is an identity:
1) cos x/ 1-sin^2x= sec x
cosx/(cos^2x) = secx
1/cosx = secx
secx = secx
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2) sec x/sin x - sin x/cos x = cot x
Multiply thru by (sinx)(cosx) to get:
(secx)(cosx) - (sinx)(sinx) = (cosx/sinx)(sinx)(cosx)
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1 - sin^2 = cos^2x
cos^2x = cos^2x
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3) 1+tan^2ø/ cos ^2ø = sec^4 ø 
sec^2x/cos^2x = sec^4x
1/cos^4x = sec^4x
sec^4x = sec^4x
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Cheers,
Stan H.