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If sinA=-4/5, and A terminates in QIV, then find sin2A

0 votes

possible answers -24/25 & -7/25.

double-angle
half-angle-identity

asked Mar 8, 2014 in TRIGONOMETRY by mathgirl Apprentice

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1 Answer

0 votes

A terminates in Q4.

SinA = opposite side/hypotenuse = -4/5

So adjacent side is 3.

CosA = adjacent side/hypotenuse = 3/5

Sin2A = 2SinACosA

= 2(-4/5)(3/5)

= -24/25

So possible answer is -24/25.

answered Mar 8, 2014 by ashokavf Scholar

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