Math Is Fun Forum

mathxyz

Member

From: Brooklyn, NY

Registered: 2024-02-24

Posts: 1,053

Similar Triangles

Triangle ABC is ~ Triangle DEF.

Triangle ABC:

angle A = 60°

angle B = 90°

angle C = 30°

Side AC = 4

Side AB = 2

Triangle DEF:

angle D = ?

angle E = ?

angle F = ?

Side DF = 8

Side DE = x

Find angles D, E, F and Side DE, which is x.

Let me see.

I haven't played with similar triangles in years. I will give it a try.

Here it is:

angle A = angle D = 60°.

angle B = angle E = 90°.

angle C = angle F = 30°.

Correct?

Side AB = Side DE = x.

Side AC = 4.

Side DF = 8.

This gives me AB/AC = DE/DF.

2/4 = x/8

4x = 2(8)

4x = 16

(1/4)(4x) = (1/4)(16)

x = 4

Is this correct?

Bob

Administrator

Registered: 2010-06-20

Posts: 10,627

Re: Similar Triangles

Yes, all correct.

Bob

---

Children are not defined by school ...........The Fonz
You cannot teach a man anything;  you can only help him find it within himself..........Galileo Galilei
Sometimes I deliberately make mistakes, just to test you!  …………….Bob

mathxyz

Member

From: Brooklyn, NY

Registered: 2024-02-24

Posts: 1,053

Re: Similar Triangles

Yes, all correct.

Bob

Really? I haven't played with geometry in decades.

Questions

1. Do you know how to do direct and indirect geometric proofs using the Statement versus Reason chart?

2. Do you know how to do geometric constructions?

If so, I will post lots of questions when we get to geometry. My main goal is learning Calculus l, ll, and lll.

Bob

Administrator

Registered: 2010-06-20

Posts: 10,627

Re: Similar Triangles

I discovered I was good at geometry when, in the year 9 exams, I got 100%. Having been subjected to physical and verbal abuse by a 'teacher' who kept telling me I was useless, I realised I could be good at something and started to work seriously.

Post on!

Bob

---

Children are not defined by school ...........The Fonz
You cannot teach a man anything;  you can only help him find it within himself..........Galileo Galilei
Sometimes I deliberately make mistakes, just to test you!  …………….Bob

mathxyz

Member

From: Brooklyn, NY

Registered: 2024-02-24

Posts: 1,053

Re: Similar Triangles

I discovered I was good at geometry when, in the year 9 exams, I got 100%. Having been subjected to physical and verbal abuse by a 'teacher' who kept telling me I was useless, I realised I could be good at something and started to work seriously.

Post on!

Bob

I can so relate to your geometry story and so can Henry Winkler for  different reasons.

Me:

1. I was told that math is not my cup of tea because Hispanics and minorities in general fear and hate math.

2. I was told that only White people, Asians and Indians are good at math.

3. This is all I needed to avoid selecting math as my major at Lehman College. I so wanted to be a math teacher. Instead, I have 3 degrees and work as a security guard making (now at the new job) $17 per hour, which at my age (59) and living in NYC is criminal, to say the least.

4. Instead, I selected Sociology with absolutely no love or interest in the field just to have a degree hanging on my wall.

5. As stated in point 3, I have 3 College degrees unrelated to mathematics.

B. S. Sociology
A. A. Liberal Arts
A. A. Religious Education/Eschatology

All of this for nothing. How about that?

Henry Winkler aka THE FONZ:

1. Henry suffers from dyslexia.

2. He was a poor student. So, his parents named him DUMB DOG as a joke but to Henry it was NOT a joke. Those two words stuck with him for the rest of his life.

3. Henry developed a fear of geometry beyond any student in his age typology.

4. Henry failed geometry 3 or 4 times in a row because he just couldn't understand the Pythygorean Theorem. In several YouTube interviews Henry talks about his fear of a^2 + b^2 = c^2.

5. Who is Henry Winkler?

A. Famous actor

B. Famous writer of children's books. The main character in his books is a cartoon with dyslexia.

C. Oscar winner

D. Great father and husband according to his wife.

E. Loved by fans worldwide EXCEPT for Tom Hanks. The two nicest guys in Hollywood don't get along. How about that?