Вычислите:в числители:cos в квадрате 22,5 градусов -sin в квадрате 22,5 в знаменатели:cos25 градусов cos20 градусов-sin25градусов sin20 градусов

Лебедев Дмитрий Сергеевич

Учитель математики

Проверено учителем

Для решения данного выражения воспользуемся тригонометрическими формулами двойного угла и косинуса суммы аргументов. 1. Анализ числителя Числитель представляет собой формулу косинуса двойного угла: cos2αsin2α=cos(2α)cosine squared alpha minus sine squared alpha equals cosine open paren 2 alpha close parenПодставим значение α=22,5alpha equals 22 comma 5 raised to the composed with power: cos222,5sin222,5=cos(222,5)=cos45cosine squared 22 comma 5 raised to the composed with power minus sine squared 22 comma 5 raised to the composed with power equals cosine open paren 2 center dot 22 comma 5 raised to the composed with power close paren equals cosine 45 raised to the composed with powerИз таблицы тригонометрических значений известно, что: cos45=22cosine 45 raised to the composed with power equals the fraction with numerator the square root of 2 end-root and denominator 2 end-fraction 2. Анализ знаменателя Знаменатель соответствует формуле косинуса суммы двух углов: cosαcosβsinαsinβ=cos(α+β)cosine alpha cosine beta minus sine alpha sine beta equals cosine open paren alpha plus beta close parenПодставим значения α=25alpha equals 25 raised to the composed with power и β=20beta equals 20 raised to the composed with power: cos25cos20sin25sin20=cos(25+20)=cos45cosine 25 raised to the composed with power cosine 20 raised to the composed with power minus sine 25 raised to the composed with power sine 20 raised to the composed with power equals cosine open paren 25 raised to the composed with power plus 20 raised to the composed with power close paren equals cosine 45 raised to the composed with powerИз таблицы тригонометрических значений: cos45=22cosine 45 raised to the composed with power equals the fraction with numerator the square root of 2 end-root and denominator 2 end-fraction 3. Вычисление итогового значения Теперь объединим полученные результаты числителя и знаменателя в одну дробь: cos222,5sin222,5cos25cos20sin25sin20=cos45cos45=1the fraction with numerator cosine squared 22 comma 5 raised to the composed with power minus sine squared 22 comma 5 raised to the composed with power and denominator cosine 25 raised to the composed with power cosine 20 raised to the composed with power minus sine 25 raised to the composed with power sine 20 raised to the composed with power end-fraction equals the fraction with numerator cosine 45 raised to the composed with power and denominator cosine 45 raised to the composed with power end-fraction equals 1 Ответ: 1 Хотите, чтобы я разобрал другие тригонометрические преобразования или помог с решением аналогичных задач?

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