A geometric and intuitive proof for the sine of the sum of two angles identity.
Published In: Mathematics Teaching, 2025, n. 297. P. 24 1 of 3
Database: Academic Search Ultimate 2 of 3
Authored By: Ghazlavi, Mostafa 3 of 3
Abstract
The article presents an alternative geometric derivation of the sine of the sum of two angles identity: sin(α + β) = sin(α) cos(β) + cos(α) sin(β). The author employs a method involving an arbitrary triangle, dividing it into two right-angled triangles to compute the area in two different ways. This approach not only confirms the identity through elementary geometry but also emphasizes the relationship between trigonometric identities and triangle geometry. Additionally, the method can be adapted for angles greater than 180° by considering supplementary angles. The author, Mostafa Ghazlavi, is a dental student and mathematics researcher from Shahid Beheshti University in Tehran, Iran. [Extracted from the article]
Additional Information
- Source:Mathematics Teaching. 2025/09, Issue 297, p24
- Document Type:Abstract
- Subject Area:Mathematics
- Publication Date:2025
- ISSN:0025-5785
- Accession Number:187993816
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