2sin (-x) * sinx=cosx на [; 5]

2sin (7π/2-x) * sinx=cosx

-2cosx*sinx-cosx=0

-cosx (2sinx+1) = 0

cosx=0⇒x=π/2+πn, n∈z

7π/2≤π/2+πn≤5π

7≤1+2n≤10

6≤2n≤9

3≤n≤4,5

n=3⇒x=π/2+3π=7π/2

n=4πx=π/2+4π=9π/2

sinx=-1/2⇒x=-π/6+2πn U x=-5π/6+2πn

7π/2≤-π/6+2πn≤5π

21≤-1+12n≤30

22≤12n≤31

11/6≤n≤31/12

n=2⇒x=-π/6+4π=23π/24

7π/2≤-5π/6+2πn≤5π

21≤-5+12n≤30

26≤12n≤35

13/6≤n≤35/12

нет решения