My Math Forum  

Go Back   My Math Forum > High School Math Forum > Algebra

Algebra Pre-Algebra and Basic Algebra Math Forum


Reply
 
LinkBack Thread Tools Display Modes
March 4th, 2013, 12:34 PM   #11
Newbie
 
Joined: Mar 2013

Posts: 8
Thanks: 0

Re: Find all the sides of this triangle.

For me.
First:
QB = PB
CQ = RC
follows that
beta = angleQBP = 2*arctg(r/QB)
gamma = angleQCR = 2*arctg(r/CQ)

AC = CB * sin (beta) / sin(180- beta - gamma) = 13

AB = CB * sin (gamma) / sin(180- beta - gamma) = 15
Plinio is offline  
 
March 4th, 2013, 01:24 PM   #12
Senior Member
 
Joined: Sep 2010

Posts: 221
Thanks: 20

Re:

Quote:
Originally Posted by skipjack
Quote:
Originally Posted by McPogor
Eventually x=12.
Incorrect. You omitted the working at precisely the point where you slipped up.
There's subtraction error: 104-90=24
Correct x=7; AC=13; AB=15
McPogor is offline  
March 4th, 2013, 04:03 PM   #13
Senior Member
 
Joined: Dec 2012

Posts: 450
Thanks: 0

Re: Find all the sides of this triangle.

Bad news for everyone.
I forgot to include the rule:don't use trignometry.
mathmaniac is offline  
March 4th, 2013, 05:12 PM   #14
Global Moderator
 
Joined: Dec 2006

Posts: 20,833
Thanks: 2161

Trigonometry isn't needed to prove Heron's formula, and hence the formula I linked to originally.
skipjack is offline  
March 4th, 2013, 05:15 PM   #15
Senior Member
 
Joined: Dec 2012

Posts: 450
Thanks: 0

Re: Find all the sides of this triangle.

I was referring to Mcpogor.
mathmaniac is offline  
March 4th, 2013, 05:28 PM   #16
Math Team
 
Joined: Oct 2011
From: Ottawa Ontario, Canada

Posts: 14,597
Thanks: 1038

Re: Find all the sides of this triangle.

No trig:
Let b = AC; then AB = b+2

Using Heron's formula:
s=(14 + b + b+2)/2 = b+8 ; leads to AreaABC = SQRT[48(b^2 + 2b - 4]

Carry on this way:
SQRT[48(b^2 + 2b - 4] = Area(triangles AOC + BOC + AOB)
Denis is offline  
March 4th, 2013, 05:30 PM   #17
Senior Member
 
Joined: Dec 2012

Posts: 450
Thanks: 0

Re: Find all the sides of this triangle.

You got it,Denis...
mathmaniac is offline  
March 4th, 2013, 05:37 PM   #18
Math Team
 
Joined: Oct 2011
From: Ottawa Ontario, Canada

Posts: 14,597
Thanks: 1038

Re: Find all the sides of this triangle.

Quote:
Originally Posted by mathmaniac
You got it,Denis...
Oh...you already knew...are you Albert's long-lost-son ? :P
Denis is offline  
March 4th, 2013, 05:40 PM   #19
Senior Member
 
Joined: Dec 2012

Posts: 450
Thanks: 0

Re: Find all the sides of this triangle.

I am an Albert fan.
And more than that these are the only sort of problems I think I can do good.....


More to come from the Albert fan....
mathmaniac is offline  
Reply

  My Math Forum > High School Math Forum > Algebra

Tags
find, sides, triangle



Thread Tools
Display Modes


Similar Threads
Thread Thread Starter Forum Replies Last Post
find the sides and angles of triangle adilgrt007 Algebra 9 August 22nd, 2013 10:25 AM
Find Remaining Angles and Sides of triangle Britwells Algebra 3 March 27th, 2013 01:31 PM
find the angles and sides of the triangle mathmaniac Algebra 16 February 14th, 2013 06:27 PM
Triangle sides...HELP MathMathHelloMath Algebra 3 October 13th, 2010 03:42 PM
Triangle sides...HELP MathMathHelloMath Calculus 1 October 13th, 2010 06:06 AM





Copyright © 2019 My Math Forum. All rights reserved.