
2.\,\cot\theta=\dfrac{\cos\theta}{\sin\theta}
![Rendered by QuickLaTeX.com [/stextbox] [stextbox caption="Trigonometric Identities" stextbox id="download"]](https://teach.sg/wp-content/ql-cache/quicklatex.com-3ec4715754f0c12389897d4c4016df3b_l3.png)
1.\,\sin^2{\theta} + \cos^2{\theta} = 12.\,\sec^2{\theta}=1+\tan^2{\theta}3.\,\text{cosec}^2{\theta}=1 + \cot^2{\theta}
![Rendered by QuickLaTeX.com [/stextbox] [stextbox caption="Addition Formulae" stextbox id="info"]](https://teach.sg/wp-content/ql-cache/quicklatex.com-e7f6b364bbea2e4164fa9ec24791de06_l3.png)
1.\,\sin(A \pm B) = \sin A\cos B \pm \cos A \sin B2.\,\cos(A \pm B) = \cos A \cos B \mp \sin A \sin B3.\,\tan(A \pm B) = \dfrac{\tan A \pm \tan B}{1 \mp \tan A \tan B}
![Rendered by QuickLaTeX.com [/stextbox] [stextbox caption="Double Angle Formulae" stextbox id="default"]](https://teach.sg/wp-content/ql-cache/quicklatex.com-c9a7b1d9a523b6821a889c80550f1051_l3.png)
1.\,\sin 2A = 2\sin A \cos A2.\,\cos2A = \cos^2A – \sin^2A= 2 \cos^2A -1= 1 – 2\sin^2A3.\,\tan 2A = \dfrac{2\tan A}{1-\tan^2A}
![Rendered by QuickLaTeX.com [/stextbox] [stextbox caption="R-Formulae" stextbox id="download"]For](https://teach.sg/wp-content/ql-cache/quicklatex.com-561243c55623e30bebb4fd104e6b7b32_l3.png)
a > 0, b > 0, 0^\circ < \alpha < 90^\circ

1.\,a\sin \theta \pm b \cos \theta = R \sin (\theta \pm \alpha)2.\,a \cos \theta \pm b \sin \theta = R \cos (\theta \mp \alpha)

R=\sqrt{a^2+b^2}, \tan\alpha=\dfrac{b}{a}$.