Improving Students’ Ability in Solving Oblique Triangles Through Concept-Base Journaling

Abstract

This study examined whether concept-based journaling improved Grade 10 students’ ability to solve problems involving oblique triangles. A pretest–posttest quasi-experimental design involved 44 students from two intact classes at Palguyod National High School during School Year 2026–2027. The experimental group (n = 23) completed structured journals after mathematics lessons for one week, identifying relevant concepts, explaining why the Law of Sines or Law of Cosines applied, documenting solution steps, analyzing errors, and reflecting on answers. The control group (n = 21) received regular instruction. A researcher-developed 30-item test, reviewed by three experts and demonstrating acceptable internal consistency (Cronbach’s α = .705), was administered before and after the intervention. The groups did not differ significantly at pretest, t(42) = 0.349, p = .729. At posttest, the experimental group (M = 17.91, SD = 3.18) outperformed the control group (M = 12.05, SD = 3.41), t(42) = −5.906, p < .001. The experimental group gained 6.04 points, t(22) = −6.251, p < .001, whereas the control group showed no significant change, mean difference = −0.24, t(20) = 0.188, p = .853. The findings indicate that structured mathematical journaling can support conceptual reasoning and problem-solving in oblique-triangle lessons, although the short intervention, intact classes, and single-school sample limit generalization.