Mister Exam

cosx=-1.2 equation

The teacher will be very surprised to see your correct solution 😉

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Numerical solution:

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The solution

You have entered [src]
cos(x) = -6/5
$$\cos{\left(x \right)} = - \frac{6}{5}$$
Detail solution
Given the equation
$$\cos{\left(x \right)} = - \frac{6}{5}$$
- this is the simplest trigonometric equation
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.
The graph
Sum and product of roots [src]
sum
0 + -re(acos(-6/5)) + 2*pi - I*im(acos(-6/5)) + I*im(acos(-6/5)) + re(acos(-6/5))
$$\left(\operatorname{re}{\left(\operatorname{acos}{\left(- \frac{6}{5} \right)}\right)} + i \operatorname{im}{\left(\operatorname{acos}{\left(- \frac{6}{5} \right)}\right)}\right) - \left(- 2 \pi + \operatorname{re}{\left(\operatorname{acos}{\left(- \frac{6}{5} \right)}\right)} + i \operatorname{im}{\left(\operatorname{acos}{\left(- \frac{6}{5} \right)}\right)}\right)$$
=
2*pi
$$2 \pi$$
product
1*(-re(acos(-6/5)) + 2*pi - I*im(acos(-6/5)))*(I*im(acos(-6/5)) + re(acos(-6/5)))
$$\left(\operatorname{re}{\left(\operatorname{acos}{\left(- \frac{6}{5} \right)}\right)} + i \operatorname{im}{\left(\operatorname{acos}{\left(- \frac{6}{5} \right)}\right)}\right) 1 \left(- \operatorname{re}{\left(\operatorname{acos}{\left(- \frac{6}{5} \right)}\right)} + 2 \pi - i \operatorname{im}{\left(\operatorname{acos}{\left(- \frac{6}{5} \right)}\right)}\right)$$
=
-(I*im(acos(-6/5)) + re(acos(-6/5)))*(-2*pi + I*im(acos(-6/5)) + re(acos(-6/5)))
$$- \left(\operatorname{re}{\left(\operatorname{acos}{\left(- \frac{6}{5} \right)}\right)} + i \operatorname{im}{\left(\operatorname{acos}{\left(- \frac{6}{5} \right)}\right)}\right) \left(- 2 \pi + \operatorname{re}{\left(\operatorname{acos}{\left(- \frac{6}{5} \right)}\right)} + i \operatorname{im}{\left(\operatorname{acos}{\left(- \frac{6}{5} \right)}\right)}\right)$$
-(i*im(acos(-6/5)) + re(acos(-6/5)))*(-2*pi + i*im(acos(-6/5)) + re(acos(-6/5)))
Rapid solution [src]
x1 = -re(acos(-6/5)) + 2*pi - I*im(acos(-6/5))
$$x_{1} = - \operatorname{re}{\left(\operatorname{acos}{\left(- \frac{6}{5} \right)}\right)} + 2 \pi - i \operatorname{im}{\left(\operatorname{acos}{\left(- \frac{6}{5} \right)}\right)}$$
x2 = I*im(acos(-6/5)) + re(acos(-6/5))
$$x_{2} = \operatorname{re}{\left(\operatorname{acos}{\left(- \frac{6}{5} \right)}\right)} + i \operatorname{im}{\left(\operatorname{acos}{\left(- \frac{6}{5} \right)}\right)}$$
Numerical answer [src]
x1 = 3.14159265358979 + 0.622362503714779*i
x2 = 3.14159265358979 - 0.622362503714779*i
x2 = 3.14159265358979 - 0.622362503714779*i
The graph
cosx=-1.2 equation