Problema Solution
find the area of an ellipse given the equation 9x^2-36x+25y^2=189
Answer provided by our tutors
Area of ellipse = πab
a: length of semi-major axis (half the length of the major axis)
b: length of semi-minor axis (half the length of the minor axis)
Re-write the ellipse in standard form first:
9x^2-36x+25y^2=189
@ y = 0,
9x^2-36x+25y^2 -189 = 0
--> 9x^2 - 36x = 189
--> x ^2 - 4x - 21 = 0
-->(x - 7)(x + 3) = 0 --> x = 7, x = -3
@ x = 0
9x^2-36x+25y^2 - 189 = 0
--> 25y^2 = 189 --> y = + or - sqrt(189/25) = 3 --> y = 3, y = -3
This gives a = 7 and b = 3. Thus, the area is:
A = πab = π(7)(3) = 21π square units.