Giải phương trình 2×cos^2+ 7×sin-7=0

What is the square root of 45? (step by step working plz)

This is about circle theorems. someone asap : (

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