Question

What is the reference angle of -960 degrees?

Answer 1

It is always possible to add, or subtract, `360°` to an angle to obtain an equivalent one. The symbol `-=` in the following passages is not a real `=`, but only an equivalent symbol.

`-960° -= -960°+360°-=-600°-=-240°-= 120°`

And `120^@` is `60^@` from the horizontal, so the reference angle for `120^@` and for the original `960^@` is `60^@`