Localized Intervention Booklet for Reinforcement of Optimum Knowledge and Mastery Level of Grade 9 Students in Trigonometry

Learning from the booklet with more worked examples is an effective learning method in well-structured domains such as Mathematics. This study examined the Localized Intervention Booklet for Reinforcement of Optimum Knowledge and Mastery Level of Grade 9 students in Panay National High School for the school year 2023-2024. It determined the significant difference between the pretest, the posttest, and the mean gain scores of the experimental and control groups. The research employed a quasi-experimental design involving 80 participants. The results showed a significant difference between the experimental and control groups' posttest scores and mean gain scores. Moreover, the overall mean percentage score of 56.63 was considered average mastery. It means that the experimental group manifested noticeable progress. The students performed well in Trigonometry. In addition, there was a significant relationship between the extent of acceptability of LIBRO and the mastery level of Grade 9 students in Trigonometry, as supported by an r-value of 0.786 with a p-value of 0.000. Moreover, the extent of the relationship between the variables was a high positive correlation. Therefore, the two groups had a positive impact of using booklets with formulas and, with several examples, improving students' mastery level, proving that using the booklet is an effective means of reaching better learning in Trigonometry. Recommendations were made to encourage the Mathematics teachers to use 'LIBRO,' a booklet with formulas and several examples, as a basis for students solving problems in Mathematics.