sin(α) +2 cos(α)= 0.3 | - sin(α)
2 cos(α)= 0.3 - sin(α) |(..)^2
4 cos^2(α)=( 0.3 - sin(α))^2
4 cos^2(α)= 0.09 -0.6 sin(α) +sin^2(α)
4 (1 -sin^2(α))= 0.09 -0.6 sin(α) +sin^2(α)
4 -4sin^2(α)= 0.09 -0.6 sin(α) +sin^2(α)
4 -5sin^2(α)= 0.09 -0.6 sin(α)
4 -5sin^2(α)- 0.09 +0.6 sin(α) =0
-5 sin^2(α)+0.6 sin(α) +3.91 =0 |:(-5)
sin^2(α)-0.12 sin(α) -0.782 =0
Substituiere: z=sin(α)
usw.