Математика: Преобразуйте в произведение sin75+sin15

Преобразуйте в произведение sin75+sin15

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Ответ:

мопс22

27.01.2021

sqrt (6) / 2

Пошаговое объяснение:

Sin (75°) + sin (15°) = 2*sin ((75°+15°) / 2) * cos ((75°-15°) / 2) = 2*sin (45°) * cos (30°) = 2 * (sqrt (2) / 2) * sqrt (3) / 2=sqrt (6) / 2

4,6(77 оценок)

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Ответ:

димон7777

27.01.2021

RECOMMENDATIONS FOR THE FORMATION OF FERTILITYSoils in the preparation of crop rotation with the ExecutiveTion methods biologizatciiTo produce systems of crop rotation on the farm must make greater use of research data. Based on materials from land arable land should be divided into homogeneous in fertility and the steepness of the slopes arrays. The most fertile lands (not been wiped out and the slightly with slopes up to 3 °) take for intensive use; arable land with an average level of fertility (low and srednesmytye with slopes of 3-5 °) - for moderate use and land with low fertility (medium and silnosmytaya arable land with a slope of more than 5 °) - limited use.On the intensive use of arable land (0-3 °) can be cultivated all cultures and have a field of pure steam.Plowing moderate use (3-5 °) is recommended to cultivate winter wheat and rye, barley, oats, peas, vetch, millet, buckwheat, sunflower and corn silage (limited, with band placement), corn for green fodder (solid seeding) , clover, sainfoin, alfalfa, perennial grasses, winter rye for green fodder, rape (winter and spring), vetch-oat and pea-oat mixture, Sudan grass and others.Plowing limited use (> 5 °) it is advisable to cultivate the following crops: winter crops (wheat, rye), barley, oats, alfalfa yellow, clover, sainfoin sandy, grassy perennial grasses, Sudan grass, and others. The most valuable arable land, not subject to erosion watershed (slope up to 1-20).This arable land should concentrate intensive cultivation of row crops and, especially, sugar beet. Saturation of cultivated crops and fallow must not exceed 50%.Certain difficulties arise when designingsystem of crop rotation on soils with the presence of salt licks. Agricultural use of alkaline complexes depends primarily on the interest in these salt licks. In the presence of salt licks to 70% complex is used as the entire land area. Their improved by chemical amelioration(Gypsum + manure), forest-steppe zone of the region it is possible with the help of earthing (applying a layer of chernozem soil 20-25 cm).Complexes with 10-30% salt licks should be used in arable land under more solontseustoychivymi crops (clover, alfalfa yellow, oats, barley, Sudan grass, sorghum, mustard, sugar beet, sunflower). In the presence of 30-50% salt lickscarried out continuous reclamation chemicalsor reclamation process followed by the introduction of fodder crop rotations.Heavy on the particle size distribution (clay)soils are more favorable for the cultivation of sugar on thembeet, wheat, barley, sunflower, peas and othercultures.Potatoes, rye, oats satisfactorilytolerate acidic soils; sunflower, sugar, fodder andbeet, wheat grow best in soils with neutral pH.On sloping lands must enter a systemcrop rotation, in which the maximum utilization of resources of soil fertility could be coupled with the achievementthe maximum effect of the anti-erosion actions culturetour. This can be achieved through the use of adaptive capacity of crops in relation to the specific soil conditions of erosion of soil and its agrochemical and agrophysical properties, hydrothermal and other conditions. Soil-protective ability of plants depends on the degree of their development and productivity. All activities aimed at increasing productivity, coupled with increased erosion control effectiveness.

4,4(48 оценок)

Ответ:

коьик1

27.01.2021

Пусть х(км/ч) скорость 1 пешехода, а у(км/ч) скорость второго. Раз они встретились через 2 часа, то оба шли по 2 часа каждый. Значит путь пройденный 1 пешеходом равен 2х(км), а путь пройденный вторым пешеходом 2у(км). Расстояние между деревнями 14,4км. получим уравнение 2х+2у=14. По условию на момент встречи один на 2км больше чем другой (например первый на 2(км) больше, значит имеем еще одно уравнение 2х-2у=2. составим и решим систему уравнений:

2х-2у=2, умножим это уравнение на (-1)

2х+2у=14,4;

-2х+2у=-2,

2х+2у=14,4;

решаем сложения

4у=12,4.

2х+2у=14,4;

у=3,1

х=4,1

ответ: 4,1км/ч и 3,1км/ч

4,6(9 оценок)

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