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( 5 8/15 - 4 7/10 ) * 2 2/3 - 5/9 = 1 2/3
1) 5 8/15 - 4 7/10 = 5 16/30 - 4 21/30 = 25/30 = 5/6
2) 5/6 * 2 2/3 = 5/6 * 8/3 = 20/9 = 2 2/9
3) 2 2/9 - 5/9 = 1 6/9 = 1 2/3
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( 5/21 + 5/6 ) * ( 1 2/3 - 3/5 ) * 1 4/5 = 2 2/35
1) 5/21 + 5/6 = 10/42 + 35/42 = 45/42
2) 1 2/3 - 3/5 = 1 10/15 - 9/15 = 1 1/15
3) 45/42 * 1 1/15 = 45/42 * 16/15 = 24/21
4) 24/21 * 1 4/5 = 24/21 * 9/5 = 72/35 = 2 2/35
CosA=(AB²+AC²-BC²)/(2AB*AC)
AB²=(1-5)²+(1-0)²+(1-0)²=16+1+1=18
AB=3√2
AC²=(3-5)²+(-1-0)²+(2-0)²=4+1+4=9
AC=3
BC²=(3-1)²+(-1-1)²+(2-1)²=4+4+1=9
BC=3
cosA=(18+9-9)/(2*3√2*3)=18/(18√2)=1/√2
A=45
Просто сокращаешь число "11"