Thread: unsure about definitions

hi
may i know why if g(r(t))=0 or constant then it implies that r'(t) (grad g) = 0 for all values of t?

Originally Posted by alexandrabel90

hi
may i know why if g(r(t))=0 or constant then it implies that r'(t) (grad g) = 0 for all values of t?

By the chain rule, . Since that measures the rate of change of g- and g doesn't change- it is equal to 0.