Plz Check my Geometry (Urgent)
posted by Ariel .
***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 don't 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.
=

1. correct
2. R=√((32)²+(4(5))²)
=10.3
3. If the endpoints are (0,1) and (18,1), it means that the circle's diameter passes through theses two points.
Therefore the diameter is(180)=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
(xx1)²+(yy1)²=r&su2p;
Therefore the answer is
(x9)²+(y1)²=9²
4. The product of the slopes of two lines intersecting at right angles is 1. You can take it from here. 
Thanks:)

Glad to be of help!

Find the area of a parallelogram with sides of 6 and 12 and an angle of 60°.