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September 21, 2014

September 21, 2014

Posted by **Evelina** on Saturday, November 12, 2011 at 10:45am.

(sina/1-cosa) + (1-cosa/sina) =

Also, wanted to ask if I did another one right:

1 - sin^2a + tg^2a * cos^2a = 1 - sin^2a + (sina/cosa)^2 * cos^2a = 1 - sin^2a + sin^2a = 1 ???

- trig -
**Steve**, Saturday, November 12, 2011 at 7:08pmThat's not what I get.

(1-cosa)/sina = tan(a/2)

so, you have

1/tan(a/2) + tan(a/2)

= (1 + tan^2(a/2))/tan(a/2)

= sec^2(a/2)/tan(a/2)

= 1/cos^2(a/2) * cos(a/2)/sin(a/2)

= 1/sin(a/2)cos(a/2) = 2/sina

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