1)sin 20°cos10°+cos20°sin10°
2)sinΠ/5cos4Π/5+cosΠ/5sin4Π/5
3)cos80°cos10°+sin80°cos10°
4)cos3Π/8sinΠ/8+cosΠ/8sin3Π/8. Решите Пожалуйста. Очень срочно

1)sin20⁰cos10⁰+cos20⁰sin10⁰==1/2[sin(20⁰+10⁰)+sin(20⁰-10⁰)]+1/2[sin(10⁰+20⁰)+sin(10⁰-20⁰)]==1/2[sin30⁰+sin10⁰]+1/2[sin30⁰+sin(-10⁰)]=sin30⁰+1/2sin10⁰-1/2sin10⁰==sin30⁰=1/2;2)sinπ/5cos4π/5+cosπ/5sin4π/5==1/2[sin(π/5+4π/5)+sin(π/5-4π/5)]+1/2[sin(4π/5+π/5)+sin(4π/5-π/5)]==1/2[sinπ+sin(-3π/5)]+1/2[sinπ+sin(3π/5]==sinπ-1/2sin(3π/5)+1/2sin(3π/5)==sinπ=0;3)cos80⁰cos10⁰+sin80⁰cos10⁰==1/2[cos(80⁰-10⁰)+cos(80⁰+10)⁰]+1/2[sin(80⁰+10⁰)+sin(80⁰-10⁰)]==1/2[cos70⁰+cos90⁰]+1/2[sin90⁰+sin70⁰]==1/2[cos70⁰+0]+1/2[1+sin70⁰]=1/2cos70⁰+1/2sin70⁰+1/2;4)cos3π/8sinπ/8+cosπ/8sin3π/8==1/2[sin(π/8+3π/8)+sin(π/8-3π/8)]+1/2[sin(3π/8+π/8)+sin(3π/8-π/8)]==1/2[sin(π/2)+sin(-π/4)]+1/2[sin(π/2)+sin(π/4)]==sin(π/2)-1/2sin(π/4)+1/2sin(π/4)=sin(π/2)=1;