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January 27, 2015

January 27, 2015

Posted by **Anonymous** on Wednesday, July 27, 2011 at 11:50am.

- maths -
**Reiny**, Wednesday, July 27, 2011 at 12:37pmDid you notice that in the first two terms the angles mentioned are complimentary angles?

And did you know that cos 70 = sin 20 ?

so....

cos70/sin20+cos57cosec33-2cos60

= cos70/sin20 + cos57/sin33 - 2cos60

= sin20/sin20 + cos57/cos57 - 2cos60

= 1+1 - 2(1/2)

= 1

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