1.

निम्नलिखित के मान ज्ञात कीजिए । `cos 105^(@)`

Answer» `cos 105^(@)=cos(60^(@)+45^(@))`
`=cos60^(@)cos 45^(@)-sin 60^(@) sin 45^(@)`
`=(1)/(2)xx(1)/(sqrt2)-(sqrt3)/(2)xx(1)/(sqrt2)=(1)/(2sqrt2)-(sqrt3)/(2sqrt2)=(1-sqrt3)/(2sqrt2)`


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