That is a round-about way to solve cos(x)=0.543 by graphing. Use the inverse function of the cosine arccos or cos^-1
If cos(x)=0.543 then
x=arccos(0.543)
To graph a trigonometric function it is more natural to use the radian as the unit. However in geometry it is more common to use the degree. To solve an equation like
x=arccos(0.543) where you want the answer to be degree, change the document settings to make the default angle unit the degree.
Make the graphing angle unit the degree and set that as default by selecting Make Default and press Enter.
×