AVweb Classic - Pelican's Perch #30: The 45-Degree Zealots
There's not a syllable in the FARs about 45-degree traffic pattern entries. Nor does the AIM require them. There exists, however, a small-but-vocal cadre of pilots — and even some FAA inspectors — who consider any other type of pattern entry (straight-in, crosswind, etc.) to be a felony.