The Philippines continues to confront a persistent challenge in raising students’ mathematical proficiency. Despite numerous interventions over the years, Filipino learners still trail behind their peers in neighboring countries. Results from the Program for International Student Assessment (PISA) 2022 revealed no significant improvement compared with the country’s performance in 2018. Fewer than one in four Filipino students achieved the minimum proficiency level in mathematics, reading, and science. Although average scores across all subjects increased slightly, the gains were limited to single-digit improvements, and overall performance remained below the OECD average. Mathematics, in particular, registered only a modest increase, rising from 353 in 2018 to 355 in 2022 (Chi, 2023). This persistent gap has been extensively documented in Philippine educational research (Valle, 2024; Ignacio & Bajet, 2025; Jaudinez, 2019; dela Cruz & Hernandez, 2023; Carandang et al., 2024; Mocorro & Mocorro, 2025; Vistro-Yu et al., 2025), with scholars underscoring the urgency of implementing more effective and sustainable solutions. In response, several studies have recommended pedagogical innovations, including the design of supplementary workbooks as instructional aids (Ibañez et al., 2021; Lomibao, 2016; Magayon & Tan, 2016; Malicoban et al., 2021; Besana et al., 2022; Ayado & Berame, 2022).

Within STEM programs, calculus occupies a pivotal position, with trigonometry serving as a foundational prerequisite. Students are expected to demonstrate mastery of trigonometric concepts, as these form the basis for higher-order mathematical reasoning in calculus and related fields. A robust grasp of trigonometric principles enables learners to approach advanced coursework with greater confidence and problem-solving capacity. However, evidence suggests that many students encounter persistent difficulties in this area. Nanmumpuni and Retnawati (2021), for example, reported that learners across a wide range of cognitive levels and creative thinking skills consistently struggled with fundamental trigonometric concepts. Their findings highlight a widespread vulnerability to errors in problem-solving, thereby underscoring the need for structured pedagogical support and targeted instructional materials.

One strategy with demonstrated effectiveness in strengthening mathematical understanding is the systematic use of workbooks (Yeh et al., 2019). Workbooks provide learners with sequenced exercises that reinforce classroom instruction and gradually build competence in complex concepts. By incorporating illustrative examples, guided practice, and progressively challenging tasks, they not only address common misconceptions but also consolidate students’ foundational knowledge. Importantly, well-designed workbooks can be adapted to diverse learning styles, offering visual, concrete, and applied problem-solving opportunities to students who may struggle with abstract reasoning (Malicoban et al., 2021; Besana et al., 2022). Furthermore, they support both independent and collaborative modes of learning: students may work at their own pace, monitor their progress, and revisit areas of difficulty, while teachers can utilize workbook outputs to diagnose learning gaps and deliver targeted feedback.

The integration of such resources into the mathematics curriculum has been shown to foster critical thinking, increase engagement, and strengthen the link between theoretical knowledge and practical application (Ayado & Berame, 2022; Rivera, 2023). Taken together, the evidence suggests that supplementing traditional instruction with research-informed, well-structured workbooks offers a pragmatic and scalable approach to addressing the persistent learning gaps of Filipino students in mathematics and trigonometry.

 

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