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January 28, 2015

January 28, 2015

Posted by **Marie** on Friday, August 3, 2012 at 3:47pm.

- Trigonometry -
**Henry**, Sunday, August 5, 2012 at 9:12pmcot(2A) = X/Y = 5/12. Q1.

r^2 = 5^2 + 12^2 = 169

r = 13.

cos(2A) = X/r = 5/13.

sin(2A) = Y/r = 12/13.

tan(2A) = Y/X = 12/5.

cos2A = 2cos^2A-1 = 5/13

2cos^2A = 5/13 + 1 = 18/13

cos^2A = 18/26

cosA = sqrt(18/26)

cosA = 3sqrt(2/26)

cosA = 3*sqrt(1/13).

sqrt = Square root.

sin(2A) = 2sinA*cosA = 12/13.

2sinA*3sqrt(1/13) = 12/13

sinA*3sqrt(1/13) = 12/26

sinA = (12/26)/(3sqrt(1/13)

sinA = (4/26)/(sqrt(1/13)

sinA = (2/13)/(sqrt(1/13)

sinA = (2/13)sqrt(1/13)/(1/13)

sinA = 2sqrt(1/13).

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