Math Is Fun Forum

aisha00

Member

Registered: 2010-12-10

Posts: 17

Urgent help with cofunction identities

Hi people. I was doin the identities chapter and im pretty much done with it except for the following, im kinda stuck with it cuz i hav no solved examples tht show how these q's r dun.

Verify the following identity

1)Cos(x-3pi/2)= -sinx

Simplify

1)Sin(x+9pi/2)

The answer is cos x

P.S-Please mention all the steps as im quite a beginner at this. Thankyou

DrSteve

Member

Registered: 2010-11-15

Posts: 10

Re: Urgent help with cofunction identities

cos(x-3pi/2)=cos x cos 3pi/2 + sin x sin 3pi/2 = (cos x)(0) + (sin x)(-1) = 0 - sin x = -sin x

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soroban

Member

Registered: 2007-03-09

Posts: 452

Re: Urgent help with cofunction identities

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