Cos2x - √ 2 *sin(п/2-x)+1=0 2. 4^x-1/2 - 17*2^x-2 + 2 больше либо равно нулю

Лебедев Дмитрий Сергеевич

Учитель математики

Проверено учителем

Решение тригонометрического уравнения Уравнение: cos2x2sin(π2x)+1=0cosine 2 x minus the square root of 2 end-root sine open paren the fraction with numerator pi and denominator 2 end-fraction minus x close paren plus 1 equals 0

  1. Применим формулы приведения и двойного угла:
    • По формуле приведения: sin(π2x)=cosxsine open paren the fraction with numerator pi and denominator 2 end-fraction minus x close paren equals cosine x . Используем формулу косинуса двойного угла: cos2x=2cos2x1cosine 2 x equals 2 cosine squared x minus 1.
  2. Подставим преобразования в исходное уравнение:
    (2cos2x1)2cosx+1=0open paren 2 cosine squared x minus 1 close paren minus the square root of 2 end-root cosine x plus 1 equals 0
    2cos2x2cosx=02 cosine squared x minus the square root of 2 end-root cosine x equals 0 Разложим на множители:
    cosx(2cosx2)=0cosine x center dot open paren 2 cosine x minus the square root of 2 end-root close paren equals 0 Решим совокупность уравнений:
    • Случай 1: cosx=0cosine x equals 0
      x=π2+πn,nZx equals the fraction with numerator pi and denominator 2 end-fraction plus pi n comma n is an element of the integers Случай 2: 2cosx2=0cosx=222 cosine x minus the square root of 2 end-root equals 0 implies cosine x equals the fraction with numerator the square root of 2 end-root and denominator 2 end-fraction
      x=±π4+2πk,kZx equals plus or minus the fraction with numerator pi and denominator 4 end-fraction plus 2 pi k comma k is an element of the integers

Ответ: x=π2+πnx equals the fraction with numerator pi and denominator 2 end-fraction plus pi n ; x=±π4+2πkx equals plus or minus the fraction with numerator pi and denominator 4 end-fraction plus 2 pi k , где n,kZn comma k is an element of the integers. Решение показательного неравенства Неравенство: 4x1/2172x2+204 raised to the x minus 1 / 2 power minus 17 center dot 2 raised to the x minus 2 power plus 2 is greater than or equal to 0

  1. Преобразуем степени к основанию 2:
    • 4x1/2=(22)x1/2=22x1=22x2=12(2x)24 raised to the x minus 1 / 2 power equals open paren 2 squared close paren raised to the x minus 1 / 2 power equals 2 raised to the 2 x minus 1 power equals the fraction with numerator 2 raised to the 2 x power and denominator 2 end-fraction equals one-half center dot open paren 2 to the x-th power close paren squared 172x2=172x22=1742x17 center dot 2 raised to the x minus 2 power equals 17 center dot the fraction with numerator 2 to the x-th power and denominator 2 squared end-fraction equals seventeen-fourths center dot 2 to the x-th power
  2. Перепишем неравенство:
    12(2x)21742x+20one-half center dot open paren 2 to the x-th power close paren squared minus seventeen-fourths center dot 2 to the x-th power plus 2 is greater than or equal to 0 Введем замену переменной:
    Пусть t=2xt equals 2 to the x-th power, где t>0t is greater than 0.
    12t2174t+20one-half t squared minus seventeen-fourths t plus 2 is greater than or equal to 0 Умножим все части на 4 для избавления от дробей:
    2t217t+802 t squared minus 17 t plus 8 is greater than or equal to 0 Найдем корни квадратного трехчлена 2t217t+8=02 t squared minus 17 t plus 8 equals 0:
    D=(-17)2428=28964=225=152cap D equals open paren negative 17 close paren squared minus 4 center dot 2 center dot 8 equals 289 minus 64 equals 225 equals 15 squared
    t1=17+154=8t sub 1 equals the fraction with numerator 17 plus 15 and denominator 4 end-fraction equals 8
    t2=17154=24=0.5t sub 2 equals the fraction with numerator 17 minus 15 and denominator 4 end-fraction equals two-fourths equals 0.5 Решим неравенство относительно tt:
    Квадратичная функция ветвями вверх, следовательно:
    t0.5t is less than or equal to 0.5 или t8t is greater than or equal to 8 Вернемся к обратной замене:
    • 2x0.52x2-1x-12 to the x-th power is less than or equal to 0.5 implies 2 to the x-th power is less than or equal to 2 to the negative 1 power implies x is less than or equal to negative 1 2x82x23x32 to the x-th power is greater than or equal to 8 implies 2 to the x-th power is greater than or equal to 2 cubed implies x is greater than or equal to 3

Ответ: x(;-1][3;+)x is an element of open paren negative infinity ; negative 1 close bracket union open bracket 3 ; positive infinity close paren. Я могу выполнить для вас отбор корней тригонометрического уравнения на заданном промежутке или составить аналогичные задания для тренировки. Что мне сделать?

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