How many unique codes are possibly formed from two characters, where the first character can be 4 to 6, and the second character can be A to D?

What is the common difference in the following arithmetic sequence 7,3,-1,-5

Simplify (1/2)4th power a. (1/16) b.(1/8) c.(1/4)

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