Geometry review

Bob · 2012-12-16 10:03:05

Whoops! Where did 'y' spring from ? I hope you mean x + x - 35 = 90.

Bob

zee-f · 2012-12-16 10:20:23

yup I mean x
So x is the large than the small angle is x-35

So x+x-35=90

x+x= 2x

-35+2x=90
-(-35) -(-35)

2x=125

x = 62.5

So the measure of the larger angle is 62.5

Bob · 2012-12-16 10:33:25

Yes. In the question post (#23) you had 62.2 I assume a typo.

Bob

zee-f · 2012-12-16 13:11:27

yeah its a typo

zee-f · 2012-12-17 01:59:02

I choose D because I didn't read the question correctly ammm but can I use the distance formula to get the answer ?

3. In the figure shown, line segment AC = CE , D is the midpoint of CE , DE=5, and BC=2 . What is the measure of AB ?

A 5
B7
C8
D10

Bob · 2012-12-17 03:12:06

hi zee-f

I've re-made the diagram with two extras: (i) I've put on the given distances; (ii) I've put a pointer to the midpoints.

You see, if AC = CE, then C is the midpoint of AE, and D is the midpoint of CE.

So start with DE = 5, and work out CE. From that answer work out AC.

Then use BC = 2 to finish the problem.

Bob

zee-f · 2012-12-17 04:10:16

DE = 5 and I know that DE is half of CE So CE would equal CD*2 So CE=10

DE=5
CD=5
CE= 10
AC= 10
So AE= 20

zee-f · 2012-12-17 04:13:05

If I say the distance from B to c is 2
then AB would be 10-2=8

Bob · 2012-12-17 06:15:38

Correct. Well done.

Did you find my diagram helpful?

When I get one of your questions, the first thing I do is to make a diagram to show the problem.

Give it a try.

Bob

zee-f · 2012-12-17 06:48:34

Yeah I sure did I drew it on my note book then found out how easy the question was I sure will try it next time

I corrected the following :
I choose D and it was incorrect
now I choose C

because adjacent angles are supplementary
AD = EH
FG=BC

So A= x
b = 180 - x

So D is X F= 180-x

So the angles are supplementary because they add up to 180
4. Which statement about angle 1 and 2 must be true?

A angle 1 is congruent to angle 2
B- 1 is the complement of angle 2
C- angle 1 is the supplement of angle 2
D- Angle 1 and 2 are vertical angles

Bob · 2012-12-17 06:51:51

C is correct.

Bob

zee-f · 2012-12-17 10:19:19

I choose A and it was incorrect still confused

Ok so Obtuse Triangle has an angle that is more than 90° So that means only one angle is more than 90° and an isosceles triangle has two equal sides and two equal angles. So am thinking the last picture

5. Which triangle is an obtuse isosceles triangle?

Bob · 2012-12-17 10:58:28

Correct!

Bob

zee-f · 2012-12-17 22:52:24

Ok first I choose B

My correction is :
area = (½)(apothem)(perimeter)

1/2 * 3.8 * 48 = 91.2

6. Calculate the area of the regular octagon shown.

A 21.9 square meters
B48.0 square meters
C91.2 square meters
D350.4 square meters

zee-f · 2012-12-17 22:55:28

I need help solving this I choose D and it was incorrect

11. Which is the contrapositive of the following statement? If quadrilateral ABCD is a rectangle, then quadrilateral ABCD is a square.

A If quadrilateral ABCD is a square, then quadrilateral ABCD is a rectangle.
B If quadrilateral ABCD is not a square, then quadrilateral ABCD is not a rectangle.
C If quadrilateral ABCD is not a rectangle, then quadrilateral ABCD is not a square.
D If quadrilateral ABCD is not a square, then quadrilateral ABCD is a rectangle.

Bob · 2012-12-18 01:06:03

hi zee-f

Q6. 91.2 That's what I get too.

Q11. Structure for a contrapositive:

If <statement A>, then <statement B> becomes if <NOT statement B>, then <NOT statement A>.

So both statements collect a NOT, and the order of statements is reversed.

The two versions are logically the same; because if B is NOT true, then A cannot be either (as A true implies B true).

Bob

zee-f · 2012-12-18 02:26:46

So A would be correct?

Bob · 2012-12-18 03:46:07

A ? Where are the NOTs ?

If <statement A>, then <statement B> becomes if <NOT statement B>, then <NOT statement A>.

Bob

zee-f · 2012-12-18 05:43:28

I thought you meant reverse the statements

So B is the answer

Bob · 2012-12-18 05:46:59

B is my answer too.

Bob

zee-f · 2012-12-18 06:08:18

8. Select which statement is true about the relationship between the measures of angle A and angle B in the diagram shown.

A The measure of angle A is greater than the measure of angle B .
B The measure of angle B is greater than the measure of angle A.
C The measure of angle A is equal to the measure of angle B .
D Cannot be determined without any other calculations.

#8- Ok so I first choose B but I still see that my answer is correct

because the measure of the missing angle would 2.38
Then I use cosine= A/H
9/11 = 0.82
cos-¹ = 34.92

So that is angle A
90+34.92=124.92
So angle B = 180 - 124.92 = 55.08

A= 34.92
B= 55.08
C= 90

Bob · 2012-12-18 06:27:57

Yes, that's ok.

My method was different but gets the same answer.

Bob

zee-f · 2012-12-18 07:42:48

So what I did isn't incorrect right? but I answered B and it was incorrect

zee-f · 2012-12-18 08:07:29

I choose B and it was incorrect still cant find the answer

16. A right circular cylinder has a base diameter of 12 meters and a height of 16 meters. What is the approximate total lateral surface area of the cylinder?

A 602.9 m²
B 829.4 m²
C 1507.2 m²
D 2034.7 m²

Bob · 2012-12-18 08:51:44

Q8. Sorry. B is correct. What I was trying to say is you could have got to the answer more quickly.
But it doesn't matter. Correct is correct however you get there.

Q16. Not B.

You need to imagine the curved surface 'unwrapped' so that you have a rectangle.

height = 16 length = circumference of the circle = pi times D area = height x circumference.

http://www.youtube.com/watch?v=gi7aaZ87EoQ

Bob

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