Find the tangent equation of the circle X & # 178; + Y & # 178; = 4 passing through point (3,0)

Let the tangent equation be y = KX + B, and the point (3,0) be substituted
0=3k+b
b=-3k
The tangent equation is
y=kx-3k
y-kx+3k=0
The distance from the center of the circle to the straight line is the radius of the circle, and the straight line is the tangent
The center coordinate is (0,0) and the radius is 2
d=│3k│/√（1+k²）=2
Move the term and square both sides
9k²=4+4k²
k=±√4/5=±2（√5）/5
The tangent equation is
y=2（√5）/5x-6（√5）/5
And y = - 2 (√ 5) / 5x + 6 (√ 5) / 5

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