Sin²105⁰-cos²105⁰=-cos(2·105⁰)=-cos210⁰=-cos(180⁰+30⁰)=cos30⁰=√3/2
1) =(5*3)³ *(3*7)² /(5*7)² *3⁴ =(5³*3³*3²*7²) /(5²*7²*3⁴) =5*3⁴ /3⁴ =5
2) (-1 4/10)³ *(3 4/7)³ =(-1 2/5 *25/7)³ =
=(7/5 *25/7)³ =5³ =125
3) (18)⁻³ *3⁷ /2⁻⁵ =(2⁵ *3⁷) /18³ =(3⁷*2⁵) /(2*3²)³ =(3⁷*2⁵) /(3^6 *2³) =3*2² =3*4 =12
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