Let $\overrightarrow{\mathrm{a}},\overrightarrow{\mathrm{b}}\text{ and }\overrightarrow{\mathrm{c}}$  be unit vectors such that  $\overrightarrow{\mathrm{a}}+\overrightarrow{\mathrm{b}}-\overrightarrow{\mathrm{c}}=0$ If the area of triangle formed by vectors  $\overrightarrow{\mathrm{a}}\text{ and }\overrightarrow{\mathrm{b}}$  is A, then what is the value of 4A²?

Given  $\overrightarrow{\mathrm{a}}+\overrightarrow{\mathrm{b}}\text{ = }\overrightarrow{\mathrm{c}}$

Now vector $\overrightarrow{\mathrm{c}}$ is along the diagonal of the parallelogram which has adjacent side vectors  $\overrightarrow{\mathrm{a}}\text{ and }\overrightarrow{\mathrm{b}}$

Since $\overrightarrow{\mathrm{c}}$ is also a unit vector, triangle formed by  vectors  $\overrightarrow{\mathrm{a}}\text{ and }\overrightarrow{\mathrm{b}}$ is an equilateral triangle. Then