Sin(п/12)+sin(5п/12)

Лебедев Дмитрий Сергеевич

Учитель математики

Проверено учителем

Для вычисления значения выражения sin(π12)+sin(5π12)sine open paren the fraction with numerator pi and denominator 12 end-fraction close paren plus sine open paren the fraction with numerator 5 pi and denominator 12 end-fraction close paren воспользуемся тригонометрической формулой суммы синусов: sin(α)+sin(β)=2sin(α+β2)cos(αβ2)sine open paren alpha close paren plus sine open paren beta close paren equals 2 sine open paren the fraction with numerator alpha plus beta and denominator 2 end-fraction close paren cosine open paren the fraction with numerator alpha minus beta and denominator 2 end-fraction close paren Пошаговое решение 1. Подстановка значений в формулу Пусть α=π12alpha equals the fraction with numerator pi and denominator 12 end-fraction и β=5π12beta equals the fraction with numerator 5 pi and denominator 12 end-fraction . Тогда: sin(π12)+sin(5π12)=2sin(π12+5π122)cos(π125π122)sine open paren the fraction with numerator pi and denominator 12 end-fraction close paren plus sine open paren the fraction with numerator 5 pi and denominator 12 end-fraction close paren equals 2 sine open paren the fraction with numerator the fraction with numerator pi and denominator 12 end-fraction plus the fraction with numerator 5 pi and denominator 12 end-fraction and denominator 2 end-fraction close paren cosine open paren the fraction with numerator the fraction with numerator pi and denominator 12 end-fraction minus the fraction with numerator 5 pi and denominator 12 end-fraction and denominator 2 end-fraction close paren 2. Вычисление аргумента синуса

  • Сумма: π12+5π12=6π12=π2the fraction with numerator pi and denominator 12 end-fraction plus the fraction with numerator 5 pi and denominator 12 end-fraction equals the fraction with numerator 6 pi and denominator 12 end-fraction equals the fraction with numerator pi and denominator 2 end-fraction Деление на 2: π/22=π4the fraction with numerator pi / 2 and denominator 2 end-fraction equals the fraction with numerator pi and denominator 4 end-fraction

3. Вычисление аргумента косинуса

  • Разность: π125π12=4π12=π3the fraction with numerator pi and denominator 12 end-fraction minus the fraction with numerator 5 pi and denominator 12 end-fraction equals negative the fraction with numerator 4 pi and denominator 12 end-fraction equals negative the fraction with numerator pi and denominator 3 end-fraction Деление на 2: π/32=π6the fraction with numerator negative pi / 3 and denominator 2 end-fraction equals negative the fraction with numerator pi and denominator 6 end-fraction

4. Подстановка вычисленных аргументов Получаем: 2sin(π4)cos(π6)2 sine open paren the fraction with numerator pi and denominator 4 end-fraction close paren cosine open paren negative the fraction with numerator pi and denominator 6 end-fraction close paren Так как косинус — четная функция ( cos(x)=cos(x)cosine negative x equals cosine x), выражение принимает вид: 2sin(π4)cos(π6)2 sine open paren the fraction with numerator pi and denominator 4 end-fraction close paren cosine open paren the fraction with numerator pi and denominator 6 end-fraction close paren 5. Подстановка табличных значений

  • sin(π4)=22sine open paren the fraction with numerator pi and denominator 4 end-fraction close paren equals the fraction with numerator the square root of 2 end-root and denominator 2 end-fraction cos(π6)=32cosine open paren the fraction with numerator pi and denominator 6 end-fraction close paren equals the fraction with numerator the square root of 3 end-root and denominator 2 end-fraction

Произведем расчет: 22232=264=622 center dot the fraction with numerator the square root of 2 end-root and denominator 2 end-fraction center dot the fraction with numerator the square root of 3 end-root and denominator 2 end-fraction equals the fraction with numerator 2 the square root of 6 end-root and denominator 4 end-fraction equals the fraction with numerator the square root of 6 end-root and denominator 2 end-fraction Ответ: 62the fraction with numerator the square root of 6 end-root and denominator 2 end-fraction Я могу также вычислить это значение в десятичном виде или решить аналогичный пример с разностью синусов. Хотите, чтобы я это сделал?

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