Question

Всё на фото...............

Answer 1

task/26548536
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25.
√12*cos²5π/12 =2√3 *(1+cos2*5π/12) /2 =√3 *(1+cos5π/6) =√3 *(1+cos(π -π/6))
√3 *(1- cosπ/6) = √3 *(1-√3 /2  )= √3 - 1,5 .
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26.
√3 - √12sin²5π/12  =√3 - 2√3( 1 -cos2*5π/12) / 2 =√3 - √3( 1 -cos5π/6)=
√3cos5π/6 = √3cos(π - π/6) = -√3cosπ/6   =  -√3*(√3)/2 = -3/2 = -1,5.
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27.
50sin19°cos19° / sin38°  =25*2sin19°cos19° / sin38° =25*sin2*19°/ sin38° =
25*sin38°/ sin38° = 25.