Question

Giá trị của biểu thức:

     sin 36\(^0\)-cos54\(^0\)+cos60\(^0\)

      sin \(^210^0\)+sin\(^230^0\)+sin\(^280^0\)+sin\(^260^0\)

 

Answer 1

a: \(\sin36^0-\cos54^0+\cos60^0\)

\(=\sin36^0-\sin36^0+\dfrac{1}{2}=\dfrac{1}{2}\)

b: \(=\left(\sin^210^0+\sin^280^0\right)+\left(\sin^230^0+\sin^260^0\right)\)

=1+1=2

Answer 2

`sin36^o -cos54^o +cos60^o`

`=cos54^o -cos54^o +cos60^o`

`=cos60^o=1/2`

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`sin^2 10^o +sin^2 30^o +sin^2 80^o +sin^2 60^o`

`=cos^2 80^o +cos^2 60^o +sin^2 80^o +sin^2 60^o`

`=(cos^2 80^2 +sin^2 80^o )+(cos^2 60^o +sin^2 60^o )`

`=1+1=2`