Sin²α-cos²α=-(cos²α-sin²α)=-cos2α
sin22,5° *sin22,5°-cos22,5° *cos22,5°=-(cos²22,5°-sin²22,5°)=-cos(2*22,5°)=
=-cos45°=-√2/2
1) 1 2/3 - 3,2 = 5/3 - 16/5 = 25/15 - 48/15 = - 23/15
2) 4,6:(-23/15) = 46/10 * (-15/23) = -3
3) -3 + 1 3/8 = -2 8/8 + 1 3/8 = -1 5/8 = -1,625
(31-12)×(32-62)=19×(-30)=-570
39 -2× = 5
-2 × = 5 - 39
- 2 × = - 3 Ч
× = 1 7
<span>y+y-25=y+10
2y-25=y+10
2y-y=10+25
y=35
</span>или так
<span>y+y-25=y+10</span>
y+y-y=10+25
y=35