Solve 2S=4+DE^2-2(4)+DEcos(1+0)

$$2 S = 4 + D E ^ { 2 } - 2 ( 4 ) + D E \cos ( 1 + 0 )$$

Solve for D

$$\left\{\begin{matrix}D=\frac{20000000000000000\left(S+2\right)}{10000000000000000E^{2}+9998476951563913E_{0}}\text{, }&E_{0}\neq -\frac{10000000000000000E^{2}}{9998476951563913}\\D\in \mathrm{R}\text{, }&S=-2\text{ and }E_{0}=-\frac{10000000000000000E^{2}}{9998476951563913}\end{matrix}\right.$$

Steps for Solving Linear Equation

Evaluate trigonometric functions in the problem

$$2 S = 4 + D E ^ {2} - 2 {(4)} + D E 0.9998476951563913$$

Multiply 2 and 4 to get 8.

$$2S=4+DE^{2}-8+DE_{0}\times 0.9998476951563913$$

Subtract 8 from 4 to get -4.

$$2S=-4+DE^{2}+DE_{0}\times 0.9998476951563913$$

Swap sides so that all variable terms are on the left hand side.

$$-4+DE^{2}+DE_{0}\times 0.9998476951563913=2S$$

Add 4 to both sides.

$$DE^{2}+DE_{0}\times 0.9998476951563913=2S+4$$

Combine all terms containing D.

$$\left(E^{2}+E_{0}\times 0.9998476951563913\right)D=2S+4$$

The equation is in standard form.

$$\left(E^{2}+\frac{9998476951563913E_{0}}{10000000000000000}\right)D=2S+4$$

Divide both sides by E^{2}+0.9998476951563913E_{0}.

$$\frac{\left(E^{2}+\frac{9998476951563913E_{0}}{10000000000000000}\right)D}{E^{2}+\frac{9998476951563913E_{0}}{10000000000000000}}=\frac{2S+4}{E^{2}+\frac{9998476951563913E_{0}}{10000000000000000}}$$

Dividing by E^{2}+0.9998476951563913E_{0} undoes the multiplication by E^{2}+0.9998476951563913E_{0}.

$$D=\frac{2S+4}{E^{2}+\frac{9998476951563913E_{0}}{10000000000000000}}$$

Divide 4+2S by E^{2}+0.9998476951563913E_{0}.

$$D=\frac{20000000000000000\left(S+2\right)}{10000000000000000E^{2}+9998476951563913E_{0}}$$