# MATH: TRIG

IF X IS AN ANGLE IN THE FIRST QUADRANT AND COSX= 3/5, FIND THE EXACT VALUE OF SIN2X

DONT UNDERSTAND, KNOW THAT THE COSX IS ON A 3,4,5 TRIANGLE

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asked by KODA
1. you should recognize the 3-4-5 right angled triangle.
so if cosx = 3/5
then sinx = 4/5

sin 2x = 2sinxcosx
= 2(4/5)(3/5) = 24/25

you can always check your result with a calculator.

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posted by Reiny

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