Sin ( pi /3+α)-1/2sin α=sin pi /3×cosα +sin α×cospi /3-1/2sin α=√3/2×cosα+
+1/2sin α-1/2sin α=√3/2×cosα
210=21×10=7×3×2×5;450=45×10=9×5×2×5;780=13×5×3×2×2
Надо привести к общему знаминатлю
1) 2х=-5
х=-2,5
2)7/5х=15
х=75/7
х=10,7
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