A museum has a -ounce piece of a precious metal. When the museum first received the piece, it had a value of $60. Its value has since decreased by 20%. What is the current value per ounce of the piece of metal?

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