[tex]\bf sin^2(\theta)+cos^2(\theta)=1\implies cos^2(\theta )=1-sin^2(\theta )
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cos(\theta )=\pm \sqrt{1-sin^2(\theta )}\\\\
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cos(x)=\pm \sqrt{1-sin^2(x)}\implies cos(x)=\pm \sqrt{1-(0.76)^2}
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cos(x)=\pm \sqrt{0.4224}\implies cos(x)\approx \pm 0.64992307[/tex]
