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# P3 Trig. watch

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1. Hi,
I'd appreciate any help on this question.

f(A)= cosA/1+sinA + 1+sinA/cosA

Prove that f(A)=2secA

I cross multiplied and attempted to put under common denominator,but i could'nt get final ans.Is this the right method?Can anyone help!!!!

Sukh.
2. (Original post by sukh_b)
Hi,
I'd appreciate any help on this question.

f(A)= cosA/1+sinA + 1+sinA/cosA

Prove that f(A)=2secA

I cross multiplied and attempted to put under common denominator,but i could'nt get final ans.Is this the right method?Can anyone help!!!!

Sukh.

Yeh it is right. Just work through it again.
3. f(A) = cosA/1+sinA + 1+sinA/cosA
f(A) = (cos^2A + 1 + 2sinA + sin^2A)/cosA(1 + sinA)

But cos^2A + sin^2A = 1, so

f(A) = (2 + 2sinA)/cosA(1 + sinA)
f(A) = 2(1 + sinA)/cosA(1 + sinA)
f(A) = 2/cosA = 2secA as required
4. Cheers people.

I made the mistake on squishy's 3rd step.I didnt simplify.

Thanks again.

Sukh.

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