<![CDATA[This study aimed to find out the mistakes made by students in doing the essay task  of the material limit and derivative, determine the cause and determine the percentage of students who make mistakes. The research is descriptive qualitative research study; the subjects were taken 5 students of class X1 TKJ SMK Kuncup Samigaluh. Data was collected through observation, tests and interviews. Data validation is done by triangulation of data by comparing the data tests and interview data, while data observations are used as reinforcement in the analysis. Data analysis techniques using qualitative data analysis including data reduction, data presentation and verification of the data and drawing. The results showed the mistakes made by the students are (1) an error in receiving information (80.77%) involved errors in writing down what is known and what is asked, cause lazy to write, forgot to write, want to get it over with, do not read the instructions carefully, (2) the error associated with. Limit and derivative concepts (92.31%) involved errors in the application of limit theorem, determine the limit algebra, trig functions to determine the derivative, find the equation of the tangent line curve, determine the interval rose functions; interval fungtion down, and the stationary value, cause students do not carefully read matter, no taboo application limit theorem, not understanding the material limit algebra indeterminate form properly, want to abbreviate the writing limxà 1, at each step, to get it over with, do not know about the herd numbers, misinterpret intent about, not careful when working, less derivative memorize trigonometric functions, forget what was asked, forgetting how to find the equation of the tangent line curve, gradient perplexed determine which ones should be used to find the equation of the tangent line perpendicular to the line of the curve, not mastering the material equation of a tangent curve, not understanding the material increasing function, decreasing function and stationary values, interval determine not understand the rules, and no way of factoring the true taboo (3) error in calculating (76.92%) involved errors in substituting algebra operations, the cause is not well understood algebra multiplication, not master nature properties of algebraic operations, while holding inaccurate, hasty in doing the task, and lack of understanding of the process of substituting the right.]]>
