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                                                                     EXHIBIT 5.1

                   Opinion of Brobeck, Phleger & Harrison LLP


October 5, 2001                                  Brobeck, Phleger & Harrison LLP
                                            Two Embarcadero Place 2200 Geng Road
                                                Palo Alto, California 94303-0913
                                                             DIRECT 650.424.0160
                                                                FAX 650.496.2885
                                                                 www.brobeck.com


Synopsys, Inc.
700 E. Middlefield Road
Mountain View, CA 94043

            Re: Synopsys, Inc. - Registration Statement for Offering of an
            Aggregate of 1,391,250 Shares of Common Stock


Dear Ladies and Gentlemen:

         We have acted as counsel to Synopsys, Inc., a Delaware corporation (the
"Company"), in connection with the registration on Form S-8 (the "Registration
Statement") under the Securities Act of 1933, as amended, of 1,391,250 shares of
the Company's common stock reserved for issuance under the Company's 1998
Nonstatutory Stock Option Plan (the "Option Plan").

         This opinion is being furnished in accordance with the requirements of
Item 8 of Form S-8 and Item 601(b)(5)(i) of Regulation S-K.

         We have reviewed the Company's charter documents and the corporate
proceedings taken by the Company in connection with the establishment and
amendment of the Option Plan. Based on such review, we are of the opinion that,
if, as and when the shares of the Company's common stock are issued and sold
(and the consideration therefor received) pursuant to the provisions of stock
option agreements duly authorized under the Option Plan and in accordance with
the Registration Statement, such shares will be duly authorized, legally issued,
fully paid and nonassessable.

         We consent to the filing of this opinion letter as Exhibit 5.1 to the
Registration Statement.

          This opinion letter is rendered as of the date first written above and
we disclaim any obligation to advise you of facts, circumstances, events or
developments which hereafter may be brought to our attention and which may
alter, affect or modify the opinion expressed herein. Our opinion is expressly
limited to the matters set forth above and we render no opinion, whether by



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implication or otherwise, as to any other matters relating to the Company, the
Option Plan or the shares of the Company's common stock issuable under such
plan.


                                                               Very truly yours,

                                             /s/ BROBECK, PHLEGER & HARRISON LLP