Fen Edebiyat Fakültesi / Faculty of Letters and Sciences Matematik - Bilgisayar / Mathematics and Computer ScienceNunokawa, M.Owa, ShigeyoshiCho, N. E.Sokół, J.Yavuz Duman, Emel2018-09-052018-09-052013-121029-242Xhttps://doi.org/10.1186/1029-242X-2013-426https://hdl.handle.net/11413/2636We estimate |Arg{p(z)}| for functions of the form p(z)=1+a1z+a2z2+a3z3+⋯ in the unit disc D={z:|z|<1} under several assumptions. By using Nunokawa’s lemma, we improve a few of Mocanu’s results obtained by differential subordinations. Some applications for strongly starlikeness and convexity are formulated.en-USNunokawa’s lemmastrongly starlike functions of order alphastrongly convex functions of order alphasubordinationArticle2-s2.0-84897615744