Help me again I’m lazy again and giving brainliest if correct number 12

The mathematical expression 9€ t means

What is the slope simplify your answer and write it as a proper fraction, improper fraction, or integer

Which sum or difference identity would you use to verify that cos (180° - q) = -cos q? a.) sin (a -b) = sin a cos b – cos a sin b b.) cos (a -b) = cos a cos b – sin a sin b c.) cos (a -b) = cos a cosb + sin a sin b d.) sin (a + b) = sin a cos b + cos a sin b