Question

How did it get 683.8?

Answer 1

9514 1404 393

Step-by-step explanation:

638.8 is the result of evaluating the expression ...

`\frac{400}{\frac{1}{\tan^2{57^\circ}}+\frac{1}{\tan^2{68^\circ}}}\approx(400)/((1)/(1.53986^2)+(1)/(2.47509^2))=(400)/(0.42173+0.163237)\\\\\\=(400)/(0.584967)=683.799\approx\boxed{683.8}`

Any scientific or graphing calculator or spreadsheet can compute this for you. (You may need to be careful to set Degrees mode for the angles.)