Posted by lungisile ntobela on Sunday, January 22, 2012 at 4:10pm.
how do you solve this.prove: cos2A plus cosA divided by sin2A minus sinA equal to cos2A plus 1 divided by sinA

math  Steve, Sunday, January 22, 2012 at 5:16pm
I think there's a typo in your equation. For example , plug in A = pi/4. You then have
(0 + 1/√2)/(1  1/√2) = (0+1)/(1/√2)
1/√2 *√2 /(√2  1) = √2
1/(√21) = √2
√2+1 = √2
However, if you fix the right side to read (cosA+1)/sinA
you have the left side:
(cos^2 A  sin^2 A + cosA)/(2sinAcosA  sinA)
(cos^2 A  (1  cos^2 A) + cosA)/(2sinAcosA  sinA)
(2cos^2 A + cosA  1)/[sinA(2cosA  1)
(2cosA1)(cosA  1)/[(2cosA  1)(sinA)]
(cosA 1)/sinA
Now if you plug in any angle, the equality holds.
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