Posted by **Ariel** on Thursday, June 10, 2010 at 11:40pm.

***I know I've posted this several times but it's like getting skipped and or no one has gone over it so I'm posting it one more time before I go to bed. I need to have these checked by tommorrow PLEASE!***

Out of 31 questions these are ones I struggled with. after the = sign is what I think the answer( except for #4, I dont know what to do at all), is so if I'm wrong can someone correct it with an explanation/formula with it please?

1.) Find the area of the parallelogram. ( base(s)=10cm, side length(s)=6cm, height=? and the angle of elevation=60'

a.)15âˆš3 cm^2

b.)30âˆš3 cm^2

c.)15âˆš2 cm^2

=30âˆš3 cm^2

2.) What is the length of the radius of a circle with the center at O(-3,4) and passes through the point P(2,-5)?

a.)9

b.)12.5

c.)10.3

=9

3.) What is the equation for a circle with a diameter having the following endpoints: N(0,1) and Q(18,1)?

a.)(x - 9)^2 + (y - 1)^2 = 81

b.)(x)^2 + (y)^2 = 72

c.)(x + 2)^2 + (y - 7)^2 = 56

=(x)^2 + (y)^2 = 72

4.) Using coordinate geometry to prove that the diagonals of a square are perpendicular to each other.

Given: Vertices are at A(0,0), B(a,0), C(a,a) and D(0,a) Slope of AC=1; Slope of BD=-1

Type your proof into the text box below.

=

- Plz Check my Geometry (Urgent) -
**MathMate**, Thursday, June 10, 2010 at 11:52pm
1. correct

2. R=√((-3-2)²+(4-(-5))²)

=10.3

3. If the end-points are (0,1) and (18,1), it means that the circle's diameter passes through theses two points.

Therefore the diameter is(18-0)=18, radius is 9.

The centre is ((0+18)/2, (1+1)/2)=(9,1).

The standard equation of a circle with radius r and passing through (x1,y1) is

(x-x1)²+(y-y1)²=r&su2p;

Therefore the answer is

(x-9)²+(y-1)²=9²

4. The product of the slopes of two lines intersecting at right angles is -1. You can take it from here.

- Plz Check my Geometry (Urgent) -
**Ariel**, Friday, June 11, 2010 at 10:36am
Thanks:)

- Plz Check my Geometry (Urgent) :) -
**MathMate**, Friday, June 11, 2010 at 11:30pm
Glad to be of help!

- Plz Check my Geometry (Urgent) -
**Anonymous**, Friday, November 19, 2010 at 9:23am
Find the area of a parallelogram with sides of 6 and 12 and an angle of 60°.

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