thank-you.....
prove:
1 - sin2A / cos2A = 1 - tanA / 1 + tan A
2007-12-03 07:42:46 · 3 answers · asked by Anonymous in Science & Mathematics ➔ Mathematics
these two quantities are identities
2007-12-03 09:14:40 · update #1
You have to change everything in SinA and CosA.
Use these identities:
Sin(2A) = 2SinACosA
Cos(2A) = (CosA)^2 - (SinA)^2
or, if you prefer:
Cos(2A) = CosACosA - SinASinA
TanA = SinA / CosA
At some point, you'll need:
(SinA)^2 + (CosA)^2 = 1
2007-12-03 07:50:28 · answer #1 · answered by Raymond 7 · 0⤊ 0⤋
RHS
= (1 -- tanA) / (1 + tanA)
= (cosA -- sinA) / ( cosA + sinA)
= (cosA -- sinA)^2 / (cosA + sinA)(cosA -- sinA)
= (cos^2A + sin^2A -- 2sinAcosA) / (cos^2A -- sin^2A)
= (1 -- sin2A) / cos2A
= LHS
2007-12-03 15:58:13 · answer #2 · answered by sv 7 · 0⤊ 0⤋
I don't believe these two quantities are identities.
2007-12-03 16:26:23 · answer #3 · answered by dave c 1 · 0⤊ 0⤋