Procedure for multiplying series

With power series represented as streams of coefficients as in exercise 3.59 , adding series is implemented by add-streams . Complete the definition of the following procedure for multiplying series:

(define (mul-series s1 s2)
  (cons-stream  (add-streams  )))

You can test your procedure by verifying that sin²x + cos²x = 1 , using the series from exercise 3.59

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