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cos3x=sin10x

Cos3x=sin ((π/2) - 3x)

sin ((π/2) - 3x) = sin10x;

sin ((π/2) - 3x) - sin10x=0.

Формула

sinα-sinβ=2sin ((α-β) / 2) ·cos ((α+β) / 2)

2sin ((π/4) - (13x/2)) ·cos ((π/4 + (7x/2)) = 0

-2sin ((13x/2) - (π/4)) ·cos ((π/4 + (7x/2)) = 0

sin ((13x/2) - (π/4)) = 0 или cos ((π/4 + (7x/2)) = 0

(13x/2) - (π/4) = πk, k∈Z или (7x/2) + (π/4) = (π/2) + πn, n∈Z

(13x/2) = (π/4) + πk, k∈Z или (7x/2) = - (π/4) + (π/2) + πn, n∈Z

x = (π/26) + (2π/13) ·k, k∈Z или x) = (π/14) + (2π/7) ·n, n∈Z