You can use GeoGebra to find the tangent line to the graph of a function at a given point: 
     GeoGebra Instruction 1
Algebra     View     and         Graphics     View     under         View     in         Menu.         Algebra     View     and         press         Enter.         Algebra     View     and         press         Enter.         Here,         .         Tangents Toolbar,         then         click         the         point,         followed         by         the         graph         you         have         made.         The         equation         for         the         tangent         will         appear         in         Algebra     View.