trigonometric identities

**robasc** · November 26th 2008, 02:00 PM

Could someone please tell me if I done this correctly?

Verify the identity
$ cot^2 x - cos^2 x = cot^2 x cos^2 x $

$ -cos^2(-x) = cos^2 x $
So:
$ cot^2 x cos^2 x $

**vincisonfire** · November 26th 2008, 03:03 PM

$ cot^2 x - cos^2 x = cot^2 x \cdot cos^2 x $
$ \frac{cos^2 x}{sin^2 x} - cos^2 x = \frac{cos^2 x}{sin^2 x} \cdot cos^2 x $
$ \frac{1}{sin^2 x} - 1 = \frac{cos^2 x}{sin^2 x} $
$ cosec^2 x = cot^2 x +1 $
The well known identity you can easily check. Multiply by $ sin^2 x $
$ 1 - sin^2 x = cos^2 x $
$ 1 = cos^2 x + sin^2 x $

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