Question #060b7

1 Answer
Jim G.
May 19, 2017

#+-1/10sqrt51#

Explanation:

#• cosA=+-sqrt(1-sin^2A)#

#rArrcosA=+-sqrt(1-(7/10)^2)#

#color(white)(rArrcosA)=+-sqrt(51/100)=+-1/10sqrt51#

#"the sign will depend on which quadrant A is in"#

#sinA>0" and so could be in the first/second quadrant"#

#"if first quadrant then " cosA=1/10sqrt51#

#"if second quadrant then " cosA=-1/10sqrt51#

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