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Grade 10Trigonometry

What is the value of cos(22.5) in roots????? WITH FULL PROCESS

Profile image of Ayush Kumar
9 Years agoGrade 10
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1 Answer

Profile image of Vaibhav Singh
9 Years ago
\cos45 = cos(2x22.5)
=> cos(2x22.5)  = \cos2(22.5) – \sin2(22.5)
= 2\cos2(22.5) -1 
=> 2\cos2(22.5) –1 = 1/\sqrt{2}
=>2\cos2(22.5) = (\sqrt{2} + 1)/\sqrt{2}
=> \cos2(22.5) = (\sqrt{2} + 1)/2\sqrt{2}
=> \cos(22.5) = \sqrt{(\sqrt{2} + 1)/2\sqrt{2}}

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