cosx/5=-(√3/2) equation
The teacher will be very surprised to see your correct solution 😉
The solution
Detail solution
Given the equation
$$\frac{\cos{\left(x \right)}}{5} = - \frac{\sqrt{3}}{2}$$
- this is the simplest trigonometric equation
Divide both parts of the equation by 1/5
The equation is transformed to
$$\cos{\left(x \right)} = - \frac{5 \sqrt{3}}{2}$$
As right part of the equation
modulo =
True
but cos
can no be more than 1 or less than -1
so the solution of the equation d'not exist.
Sum and product of roots
[src]
/ / ___\\ / / ___\\ / / ___\\ / / ___\\
| |-5*\/ 3 || | |-5*\/ 3 || | |-5*\/ 3 || | |-5*\/ 3 ||
- re|acos|--------|| + 2*pi - I*im|acos|--------|| + I*im|acos|--------|| + re|acos|--------||
\ \ 2 // \ \ 2 // \ \ 2 // \ \ 2 //
$$\left(\operatorname{re}{\left(\operatorname{acos}{\left(- \frac{5 \sqrt{3}}{2} \right)}\right)} + i \operatorname{im}{\left(\operatorname{acos}{\left(- \frac{5 \sqrt{3}}{2} \right)}\right)}\right) + \left(- \operatorname{re}{\left(\operatorname{acos}{\left(- \frac{5 \sqrt{3}}{2} \right)}\right)} + 2 \pi - i \operatorname{im}{\left(\operatorname{acos}{\left(- \frac{5 \sqrt{3}}{2} \right)}\right)}\right)$$
$$2 \pi$$
/ / / ___\\ / / ___\\\ / / / ___\\ / / ___\\\
| | |-5*\/ 3 || | |-5*\/ 3 ||| | | |-5*\/ 3 || | |-5*\/ 3 |||
|- re|acos|--------|| + 2*pi - I*im|acos|--------|||*|I*im|acos|--------|| + re|acos|--------|||
\ \ \ 2 // \ \ 2 /// \ \ \ 2 // \ \ 2 ///
$$\left(\operatorname{re}{\left(\operatorname{acos}{\left(- \frac{5 \sqrt{3}}{2} \right)}\right)} + i \operatorname{im}{\left(\operatorname{acos}{\left(- \frac{5 \sqrt{3}}{2} \right)}\right)}\right) \left(- \operatorname{re}{\left(\operatorname{acos}{\left(- \frac{5 \sqrt{3}}{2} \right)}\right)} + 2 \pi - i \operatorname{im}{\left(\operatorname{acos}{\left(- \frac{5 \sqrt{3}}{2} \right)}\right)}\right)$$
/ / / ___\\ / / ___\\\ / / / ___\\ / / ___\\\
| | |-5*\/ 3 || | |-5*\/ 3 ||| | | |-5*\/ 3 || | |-5*\/ 3 |||
-|I*im|acos|--------|| + re|acos|--------|||*|-2*pi + I*im|acos|--------|| + re|acos|--------|||
\ \ \ 2 // \ \ 2 /// \ \ \ 2 // \ \ 2 ///
$$- \left(\operatorname{re}{\left(\operatorname{acos}{\left(- \frac{5 \sqrt{3}}{2} \right)}\right)} + i \operatorname{im}{\left(\operatorname{acos}{\left(- \frac{5 \sqrt{3}}{2} \right)}\right)}\right) \left(- 2 \pi + \operatorname{re}{\left(\operatorname{acos}{\left(- \frac{5 \sqrt{3}}{2} \right)}\right)} + i \operatorname{im}{\left(\operatorname{acos}{\left(- \frac{5 \sqrt{3}}{2} \right)}\right)}\right)$$
-(i*im(acos(-5*sqrt(3)/2)) + re(acos(-5*sqrt(3)/2)))*(-2*pi + i*im(acos(-5*sqrt(3)/2)) + re(acos(-5*sqrt(3)/2)))
/ / ___\\ / / ___\\
| |-5*\/ 3 || | |-5*\/ 3 ||
x1 = - re|acos|--------|| + 2*pi - I*im|acos|--------||
\ \ 2 // \ \ 2 //
$$x_{1} = - \operatorname{re}{\left(\operatorname{acos}{\left(- \frac{5 \sqrt{3}}{2} \right)}\right)} + 2 \pi - i \operatorname{im}{\left(\operatorname{acos}{\left(- \frac{5 \sqrt{3}}{2} \right)}\right)}$$
/ / ___\\ / / ___\\
| |-5*\/ 3 || | |-5*\/ 3 ||
x2 = I*im|acos|--------|| + re|acos|--------||
\ \ 2 // \ \ 2 //
$$x_{2} = \operatorname{re}{\left(\operatorname{acos}{\left(- \frac{5 \sqrt{3}}{2} \right)}\right)} + i \operatorname{im}{\left(\operatorname{acos}{\left(- \frac{5 \sqrt{3}}{2} \right)}\right)}$$
x2 = re(acos(-5*sqrt(3)/2)) + i*im(acos(-5*sqrt(3)/2))
x1 = 3.14159265358979 + 2.14513586791928*i
x2 = 3.14159265358979 - 2.14513586791928*i
x2 = 3.14159265358979 - 2.14513586791928*i