SOLUTION: If cos(x)=1/18 (in Quadrant-I), find sin(2x)=

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Question 1158166: If cos(x)=1/18
(in Quadrant-I), find sin(2x)=
Answer by josmiceli(19441) About Me  (Show Source):
You can put this solution on YOUR website!
+sin%28+2x+%29+=+2sin%28x%29%2Acos%28x%29+
+cos%28+x+%29+=+1%2F18+
+sin%5E2%28x%29+=+1+-+cos%5E2%28x%29+
+sin%5E2%28x%29+=+1+-+%28+1%2F18+%29%5E2+
+sin%5E2%28x%29+=+1+-+1%2F324+
+sin%5E2%28x%29+=+323+%2F+324+
+sin%28x%29+=+17.9722+%2F+18+
+sin%28x%29+=+.9985+
-------------------------
+sin%28+2x+%29+=+2sin%28x%29%2Acos%28x%29+
+sin%28+2x+%29+=+2%2A.9985%2A%28+1%2F18+%29+
+sin%282x%29+=+.1109+
--------------------------
check with calculator:
+cos%28+x+%29+=+1%2F18+
+cos%28+x+%29+=+.05556+
+x+=+86.8153+ degrees
+2x+=+173.6305+
+sin%28+2x+%29+=+.1109+
OK