Ihad this uncanny need to look good all the time and i used to follow a skincare regimen but after i - id344885020220814 от 1к3к5к7к 14.08.2022 03:13

Question

Алгебра: Ihad this uncanny need to look good all the time and i used to follow a skincare regimen but after i turned 30, those diys stopped working. whatever i applied to my face just didn’t work and then i realized my skin needs something more. i decided to consult a friend who is a dermatologist and she recommended a product called miracle ritual cream to me. although i am partial to diys and home made creams but this time i decided to do what my friend suggested. she told me to bring about av few changes

1к3к5к7к · Accepted Answer

1. Разложим cos 4x по формуле 2-г угла получим
cos 4x = 1 - 2 sin^2 2x
2.Свернем 26 sin x cos x по формуле 2-го угла для sin и получим
13 sin 2x
3.Теперь наше уравнение выглядит как
13 sin 2x - (1 - 2 sin^2 2x) + 7 = 13 sin 2x - 1 + 2 sin^2 2x + 7 = 2 sin^2 2x + 13 sin 2x + 6 = 0
Делаем замену t = sin 2x t^2 = sin^2 2x
4.Получаем квадратное уравнение
2t^2 + 13t + 6 = 0
Находим корни
t1 = -0.5
t2 = 6

так как sin 2x может быть только -0.5 считаем корень для этого значения

sin 2x = -1/2
2x = (-1^n) * arcsin(-1/2) + pin, n∈Z
2x = (-1^n+1) * arcsin(1/2) + pin, n∈Z - здесь мы убрали минус из под arcsin

ответ : x = (-1^n+1) * pi/6 + pin/2, n∈Z

Надеюсь объяснил подробно!)

MOGZ ответил