The high school pass rate, for mathematics, in South Africa is very low. This is particularly so in trigonometry functions. One of the possible factors leading to this is the traditional method of teaching and learning. This study was undertaken to determine whether the use of Information and Communication Technology (ICT) would influence students’ learning of trigonometry functions. In order to answer this question the teaching and learning instructions developed were based on activity theory (AT) and action, process, object, and schema (APOS) theory. The study followed a non-equivalent control group, quasi-experimental design with a pre- post-test approach. Since it was not possible to randomly select participants for the study, intact groups were used. There were two groups: a control and an experimental one. Both groups wrote a standardized achievement pre-test to establish their comparability at the beginning of the study. While the control group was taught in the traditional way (grade 10-12 syllabus), the experimental group used the software Geogebra. The computer software (Geogebra) and the South African grade 10-12 syllabus for trigonometry functions were used during the lessons of the experimental group. At the end of the study, a similar post-test was administered on both groups to measure the comparative effects of either of the teaching methods on the performance of students. A t-test independent sample statistical analysis was performed on the findings using a statistics package, SPSS. The results of this investigation indicated that the use of the computer software, Geogebra, in the teaching and learning of trigonometry functions improved the performance of the Grade 12 students. / Mathematics Education / M. Sc. (Mathematics Education)