Hi, If you help me it basically means you saved my life!
1. Find the distance (3,4) between and the line 4x+3y+7=0.
2. Find the distance between the graphs of 5x-12y+45=0 and 5x-12y-46=0.
3. A circle centered at the origin is tangent to the line x-y+4=0. What is the area of the circle?
THANK YOU!
1.
There may be several ways to do this, but one of the easier ways is through the "formula" for finding the distance between a point and aline
If (m, n) is the point and Ax + BY + C = 0 is the equation of the line....the distance is given by
l Am + Bn + C l l 4(3) + 3(4) + 7 l l 31 l 31
______________ = __________________ = _______ = ___ = 6.2 units
√ [ A^2 + B^2 ] √ [ 4^2 + 3^2 ] √ 25 5
2.
5x-12y+45=0 and 5x-12y-46=0
12y = 5x + 45 and 12y = 5x - 46
y = (5/12)x + 45/12
y = (5/12) x + 15/4
These lines have the same slope.......the first line has a y intercept at 15/4....
So the point (0, 15/4) is on the first line
The distance between this point and the second line is the perpendicular distance between both lines...so we have
l 5(0) - 12 (15/4) - 46 l l -12 (15/4) - 46 l l -91 l 91
____________________ = ________________ = ______ = ___ = 7 units
√ [ 5^2 + 12^2 ] √ [ 169 ] 13 13
3. A circle centered at the origin is tangent to the line x-y+4=0. What is the area of the circle?
Since the circle is centered at (0,0) a radius drawn from this point will be perpendicular to this line at the point of tangency....and this will be the shortest distance from (0,0) to this line....so.....this distance is given by
l 1 (0) - 1 (0) + 4 l 4 4√2 2√2 = √8 units = radius of the circle
________________ = ___ = ____ =
√ [1^2 + 1^2 l √2 2
So....the area of the circle = pi * radius ^2 = pi * ( √8)^2 = 8 pi units^2