Why are index fossils helpful to geologists? They tell the absolute age of the rock they occur in
They tell the age of many different rock layers
They tell the age of rocks at one location only
They tell the relative age of rock in which they occur

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