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                                                                     EXHIBIT 5.1




                                February 4, 1997


Securities and Exchange Commission
Judiciary Plaza
450 Fifth Street, N.W.
Washington, DC  20549

         RE:      SYNOPSYS, INC.
                  REGISTRATION STATEMENT ON FORM S-4

Ladies and Gentlemen:

         This opinion is furnished to you in connection with a Registration
Statement on Form S-4 (the "Registration Statement") filed with the Securities
and Exchange Commission (the "Commission") under the Securities Act of 1933, as
amended, for the registration of 12,148,677 shares of Common Stock (the "Common
Stock"), $.01 par value per share, of Synopsys, Inc. (the "Company").

         We have acted as counsel for the Company in connection with the
issuance of the shares of Common Stock pursuant to an Agreement and Plan of
Merger (the "Merger Agreement"), dated as of January 16, 1997, by and among the
Company, EPIC Merger Co., Inc. and EPIC Design Technology, Inc. We have examined
signed copies of the Registration Statement and all exhibits thereto (including,
but not limited to, the Merger Agreement), all as filed with the Commission. We
have also examined and relied upon the original or copies of minutes of meetings
of the stockholders and Board of Directors of the Company, a certificate of the
transfer agent for the Common Stock, the Certificate of Incorporation and the
Bylaws of the Company and such other documents as we have deemed material to the
opinion set forth below.

         Based upon the foregoing, we are of the opinion that the shares of
Common Stock to be issued pursuant to the Merger Agreement are duly authorized
by the Company and, when issued in accordance with the terms of the Merger
Agreement, will be validly issued, fully paid and non-assessable.

         We hereby consent to the filing of this opinion as an exhibit to the
Registration Statement and to the use of our name wherever it appears in the
Registration Statement and in the related Prospectus, as originally filed or 
as amended or Supplemented.

         This opinion is to be used only in connection with the issuance of the
Common Stock while the Registration Statement is in effect.

                                            Very truly yours,


                                            /s/ GRAY CARY WARE & FREIDENRICH
                                            GRAY CARY WARE & FREIDENRICH
                                            A Professional Corporation