$4\mathrm{.}6$ Vector $\frac{?}{\text{b}\text{a}\text{r}}(R)$ in Figure $4\mathrm{.}9$ is the difference between vectors $\frac{?}{\text{b}\text{a}\text{r}}(T)$ and $\frac{?}{\text{b}\text{a}\text{r}}(S).$ If $\frac{?}{\text{b}\text{a}\text{r}}(S)$ is inclined at $25$ from the vertical and the angle

between $\frac{?}{\text{b}\text{a}\text{r}}(S)$ and $\frac{?}{\text{b}\text{a}\text{r}}(T)$ is $35,$ calculate the magnitude and direction of vector $\frac{?}{\text{b}\text{a}\text{r}}(R).$ The magnitudes of $\frac{?}{\text{b}\text{a}\text{r}}(S)$ and $\frac{?}{\text{b}\text{a}\text{r}}(T)$ are $21$ cm and $38$ cm$,$

respectively.

Figure $4\mathrm{.}9$