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# Chapter 10 C2 help Watch

1. Prove that 1/cosA - cosA = sinAtanA
1/(sinA/tanA) - sinA/tanA
tanA/sinA - sinA/tanA
TanA/sinAtanA - sinA/sinAtanA
sinA - tanA

Where have i gone wrong?
sorry if this is hard to read
2. (Original post by physicshelpme)
Prove that 1/cosA - cosA = sinAtanA
1/(sinA/tanA) - sinA/tanA
tanA/sinA - sinA/tanA
TanA/sinAtanA - sinA/sinAtanA
sinA - tanA

Where have i gone wrong?
sorry if this is hard to read
Just get a common denominator on the LHS.
That will leave you 1-cos^2(A)/cos(A)

What does that now give?.......
3. (Original post by physicshelpme)
Prove that 1/cosA - cosA = sinAtanA
1/(sinA/tanA) - sinA/tanA
tanA/sinA - sinA/tanA
TanA/sinAtanA - sinA/sinAtanA
sinA - tanA

Where have i gone wrong?
sorry if this is hard to read
You should have combined the LHS, and then proceeded to show that it equals the RHS.

4. Also, in your third line, you can't just randomly multiply everything by 1/tan(A) and 1/sin(A). Whatever you do to the bottom, you have to do to the top.
5. (Original post by Indeterminate)
You should have combined the LHS, and then proceeded to show that it equals the RHS.

why does it become b^2?
6. (Original post by physicshelpme)
why does it become b^2?
actually i understand, thank you

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