Отбросьте все члены которые по модулю, меньше 0,001. Р.S. <span><span><span><span><span>(<span>cos<span>(<span>x2</span>)</span></span>)</span>′</span>=−2xsin<span>(<span>x2</span>)</span></span><span>cos<span>(<span>x2</span>)</span>=1−<span>x2</span><span>(<span>2ξsin<span>(<span>ξ2</span>)</span></span>)</span>=1−xξsin<span>(<span>ξ2</span>)</span>,0<ξ<0,2</span><span><span>∫0<span>0,2</span></span><span>cos<span>(<span>x2</span>)</span>dx</span>=0,2−0,5<span><span>(<span>0,2</span>)</span>2</span>ξsin<span>(<span>ξ2</span>)</span></span><span>0,5<span><span>(<span>0,2</span>)</span>2</span>ξsin<span>(<span>ξ2</span>)</span><0,5<span><span>(<span>0,2</span>)</span>3</span><0,001</span></span><span><span><span><span>(<span>cos<span>(<span>x2</span>)</span></span>)</span>′</span>=−2xsin<span>(<span>x2</span>)</span></span><span>cos<span>(<span>x2</span>)</span>=1−<span>x2</span><span>(<span>2ξsin<span>(<span>ξ2</span>)</span></span>)</span>=1−xξsin<span>(<span>ξ2</span>)</span>,0<ξ<0,2</span><span><span>∫0<span>0,2</span></span><span>cos<span>(<span>x2</span>)</span>dx</span>=0,2−0,5<span><span>(<span>0,2</span>)</span>2</span>ξsin<span>(<span>ξ2</span>)</span></span><span>0,5<span><span>(<span>0,2</span>)</span>2</span>ξsin<span>(<span>ξ2</span>)</span><0,5<span><span>(<span>0,2</span>)</span>3</span><0,001</span></span></span>
Поэтому <span><span><span>∫0<span>0,2</span></span><span>cos<span>(<span>x2</span>)</span>dx</span>≈0,2</span></span>
Обозначим скорость встречного поезда через Х. Тогда суммарная скорость (40 +Х) км/час Время наблюдения равно длине поезда деленное на суммарную скорость. Выразим все в часах и километрах. 0,075/(Х+40) = 3/3600 (В часе 3600сек.) 0,075х3600=(Х+40)х3 Х=50км/час.
