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Find the value of cos 75
Find the value of cos 75

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6 years ago

```							cos75=cos(90-15)=sin15sin^@=(1-cos(2@))/2sin^15=(1-cos30)/2=(1-(sqrt(3))/2)/2=(2-sqrt3)/4sin15=sqrt(2-sqrt3)/2hence cos75=sqrt(2-sqrt3)/2  Ans.Thanks & RegardsRinkoo GuptaAskIITians Faculty
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6 years ago
```							Simply using, cos 2A = 2 cos^2 A - 1
For A = 75, cos 150 = 2cos^2 75 - 1 = - cos 30
So, cos^2 75 = 1 - cos 30 = (2-sqrt3)/2x2

Hence, cos 75 = sqrt( (2-sqrt3) ) / 2
```
6 years ago
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