Question 813098
Find the set of values of x (in radians) for which cos(x) = &#8722;1/sqrt(2), for x in [&#8722;2&#960;, 0].
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cosx=-1/&#8730;2=-&#8730;2/2
reference angle x in quadrants II and III where cos<0
x=-3&#960;/4,-5&#960;/4
note: cos is an even function,ie,cos(x)=cos(-x)