Question

can we write sin 225 degree as sin[ 90+ 90+ 45]

Answer 1

$$\begin{gathered} \mathrm{Yes},\mathrm{we}\mathrm{can}\mathrm{write}\sin 225\mathrm{as}\sin \left(90+90+45\right). \\ \mathrm{So}, \\ \sin 225=\sin \left(90+90+45\right) \\ =\sin \left(90+\left(90+45\right)\right) \\ =\cos \left(90+45\right) \\ =-\sin 45 \\ =\frac{1}{\sqrt{2}} \\ \Rightarrow \mathbf{sin}\mathbf{225}\mathbf{=}\frac{\mathbf{1}}{\sqrt{\mathbf{2}}} \end{gathered}$$