300 * 15% = 300 * 0,15 = 45 кг - сметаны
ответ. Из 300 кг молока получили 45 кг сметаны.
6.
sin51°cos39°-sin21°cos9°=sin(90°-39°)cos39°-sin21°cos9<span>°=
=cos39</span>°cos39°-sin(30°-9°)cos9°=cos²39°-sin(30°-9°)cos9<span>°=
=(cos(30</span>°+9°))² - (sin30°cos9°-cos30°sin9°)cos9<span>°=
=(cos30</span>°cos9°-sin30°sin9°)² - (¹/₂ cos9° - (√3/2) sin9°)cos9<span>°=
=((</span>√3/2) cos9° - ¹/₂ sin9°)² - ¹/₂ cos² 9° + (√3/2) sin9° cos9<span>° =
= </span>³/₄ cos² 9° - (√3/2)sin9° cos9° + ¹/₄ sin² 9° - ¹/₂ cos² 9° + +(√3/2)sin9°cos9<span>°=
= </span>³/₄ cos² 9° - ²/₄ cos² 9° + ¹/₄ sin² 9<span>° =
= </span>¹/₄ cos² 9° + ¹/₄ sin² 9<span>° =
= </span>¹/₄ (cos² 9° + sin² 9<span>°</span>)= ¹/₄ * 1 = ¹/₄
0.41 x + 3.5x - 15.63 ; x=10
0.41 * 10 + 3.5 * 10 - 15.63 = <span><u><em>23,47</em></u></span>
<span>1) 0.41 * 10 = 4,1</span>
2) 3.5 * 10 = 35
3) 4,1 + 35 = 39,1
4) 39,1 - 15,63 = 23,47