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Using the formula,cos A=√1+cos2A/2, find the …

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Using the formula,cos A=√1+cos2A/2, find the value of cos 30°,it being given that cos 60°=1/2

Posted by Sanjay Tyagi 6 years, 3 months ago

CBSE > Class 10 > Mathematics

1 answers

Sia ? 6 years, 3 months ago

Given formula : cos A = {tex}\sqrt{1}{/tex} + {tex}\frac {cos2A}{2}{/tex}
Also, cos60 = {tex}\frac {1}{2}{/tex}
Required to find : cos30
Now,
Let A = 30^o, 2A = 60^o
cosA = {tex}\sqrt{1}{/tex} + {tex}\frac {cos2A}{2}{/tex}
cos30= {tex}\sqrt{( } 1+1 / 2) / 2{/tex}
cos30 = {tex}\sqrt{( } 3 / 2) / 2{/tex}
cos30 = {tex}\sqrt {(\frac {3}{4})} =\sqrt \frac {3}{2}{/tex}
Therefore, {tex}\cos 30=\frac{\sqrt{3}}{2}{/tex}

2Thank You

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Posted by Kanika . 1 month ago

CBSE > Class 10 > Mathematics

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sin60° cos 30°+ cos60° sin 30°

Posted by Vanshika Bhatnagar 1 year, 4 months ago

CBSE > Class 10 > Mathematics

2 answers

Don't post personal information, mobile numbers and other details.
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Posted by Hari Anand 6 months, 1 week ago

CBSE > Class 10 > Mathematics