Question

How do I solve sin 2x = 10/4?

Answer 1

sin 2x = 10/4
sin 2x = 2.5
\[2x = \sin^-1(2.5)\]

Answer 2

You use the inverse function of sin, the arcsin function, it has the property
\[ \arcsin(\sin(x))=x \]
So that
\[ \arcsin(\sin(2x))=2x=\arcsin\left(\frac{10}{4}\right) \\
x=\frac{1}{2}\arcsin(2.5) \]