What is the relationship between the sine and cosine of complementary angles? how do we know it is true?

What is the missing step in this proof ?

The square root of 9x plus 7 plus the square rot of 2x equall to 7

Afair survey question is one that does not encourage biased responses. which survey question is fair? a.) do you agree that only unethical people take credit for other people’s work? b.) have you ever taken credit for somebody else’s work? c.) have you ever engaged in unethical behavior, such as taking credit for somebody else’s work? d.) don’t you think it is unethical to take credit for somebody else’s work?