Eliminate the parameter, t, in the parametric equations, x = 2cost and y = 4sint. x2 + y2 = 4 x2 + y2 = 16 4x2 + y2 = 16 x2 + 2y2 = 16

4x^2 + y^2= 16

Step-by-step explanation:

x= 2cost

y=4sint

x= x/2

y=y/4

use equation;

sin^2x + cos^2x= 1

replace:

(y/4)^2 + (x/2)^2=1

y^2/16 + x^2/4= 1

y^2+4x^2/16=1

y^2+x^2=16

rearrange:

4x^2 + y^2= 16

  21.3

step-by-step explanation:

multiplying the given equation by c/sin(25°), we get

  c = 9/sin(25°) ≈ 21.2958 ≈ 21.3

we assume "c" is the length of ab, the side opposite angle c in triangle abc.