Double Angle Formula

The double angle formulae give trigonometric ratios of $2A$ in terms of ratios of $A$, for example $\sin 2A=2\sin A\cos A$ and $\cos 2A=\cos^{2}A-\sin^{2}A$. They come from the addition formulae with $B=A$ and are widely used to simplify expressions and solve equations.

You meet Double Angle Formula in the Trigonometric Functions chapter of SPM Additional Mathematics. Knowing the term precisely matters in the exam: questions often hinge on reading a keyword correctly, and because SPM marking is analytic, using the right definition in your working helps secure method marks.

Our teachers make sure a student can not only recite what Double Angle Formula means but use it fluently in a full solution.

Because the SPM Add Math paper is bilingual (BM/EN), it helps to know this term in each language: Double Angle Formula (EN) · Rumus Sudut Berganda (BM) · 倍角公式 (中文)

Other key terms from the Trigonometric Functions chapter you may want to check:

• Reciprocal Trigonometric Ratios
• Reference Angle
• Amplitude
• Period
• Trigonometric Identity
• Addition Formula