The sum and difference of two perpendicular vectors of equal lengths are,

What are the $x$ and $y$ components of a $25 \mathrm{m}$ displacement which is at an angle of $210°$ with the $x$-axis (anti-clockwise)?

One of the rectangular components of a velocity of $60 \mathrm{km} {\mathrm{h}}^{-1}$ is $30 \mathrm{km} {\mathrm{h}}^{-1}$. The other rectangular component is $x\sqrt{3} \mathrm{km} {\mathrm{h}}^{-1}$. Find $x$.

If $0.5\hat{\mathrm{i}}+0.8\hat{\mathrm{j}}+c\hat{\mathrm{k}}$ is a unit vector, find the value of $\pm c\frac{10}{\sqrt{11}}$.