What is the exact value for cos(-2/3)?
this should be done without a calculator.
explain the process if possible.

Notice the picture below

see where that angle is?

check your Unit Circle for that value

also notice, that fractions of  are just like grabbing 180 degrees and splitting it, so one third of 180 or is 180/3 or 60 degrees

Idon’t know but you’ll figure it out