Explain why the value of [cosX, sinX]*[cos(90+X), sin(90+X)] is independent of X.
X=theta
what does independent of X even mean?
i suppose you mean the dot product here? just take the dot product and use the addition formula for the functions in the second pair of brackets and simplify
it means that it does not matter what X is, the value will be the same no matter what X we choosewhat does independent of X even mean?