Math Is Fun Forum

I answered D it was correct that was my last lesson in geometry I got a 9/10 in that lesson and still waiting for my final course grade thank you guys!!! ur always the best in helping

yup A was correct but I got 2 incorrect #6, #8

6. Calculate the area of the regular octagon shown.
6.B
  I choose B because area = (½)(apothem)(perimeter)
1/2 * 3.8 * 48 = 91.2
 

 
8.I still think it is B I cant really find what I did incorrect for this one I really need a clue.
I used the Pythagoras to get the missing side I got  2.38 Then I used 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

I still get B

2×(36×pi)+603.2 = 829.39

36pi is the circle area
then the area of the triangle is=  12pi( circumference of the circle ) * (16) = 192PI or 603.2

SA = 2×(36×pi)+603.2 = 829.39

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

I thought you meant reverse the  statements

So B is the answer

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.

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?

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

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

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

I choose B because Complementary angles are two angles whose measures total 90 degrees.

90 - 35 = 55 and it was incorrect.

1. Two angles are complementary. The smaller angle is 35°   less than the larger angle. What is the measure of the larger angle?

A- 27.5°   
B- 55°
C- 62.2°
D- 125°

Thank you