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प्रश्न
Find the value of cos 105°.
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उत्तर
cos 105° = cos(60° + 45°)
= [cos 60° cos 45° – sin 60° sin 45°]
= `[1/2*1/sqrt2-sqrt(3)/2*1/sqrt(2)]`
= `(1-sqrt3)/(2sqrt2)`
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