δ μ =arctan( μ ″ r μ ′ r ) MathType@MTEF@5@5@+=feaagCart1ev2aqatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbuLwBLnhiov2DGi1BTfMBaeXatLxBI9gBaerbbjxAHXgarqqtubsr4rNCHbGeaGqipG0dh9qqWrVepG0dbbL8F4rqqrVepeea0xe9LqFf0xc9q8qqaqFn0lXdHiVcFbIOFHK8Feea0dXdar=Jb9hs0dXdHuk9fr=xfr=xfrpeWZqaaeqabiGaciGacaqadmaadaqaaqaaaOqaaiabes7aKnaaBaaaleaacqaH8oqBaeqaaOGaeyypa0JaaeyyaiaabkhacaqGJbGaaeiDaiaabggacaqGUbWaaeWaaeaadaWcaaqaaiqbeY7aTzaagaWaaSbaaSqaaiaabkhaaeqaaaGcbaGafqiVd0MbauaadaWgaaWcbaGaaeOCaaqabaaaaaGccaGLOaGaayzkaaaaaa@46E3@