# SolidMensuration

• Jul 19th 2010, 05:11 AM
cutiemike1
SolidMensuration
Questions from Kern and Bland pp8 #'s 17,19,21

http://i104.photobucket.com/albums/m...ike1/num17.jpg

19. The base of an isosceles triangle is 16 in. and the altitude is 15 in. Find the radius of the inscribed circle.

http://i104.photobucket.com/albums/m...ike1/num21.jpg

in #17 about the race track i can't read clearly the value of SC = ..... maybe perhaps it is too old copy.. ^^
• Jul 19th 2010, 06:50 AM
Wilmer
What are you asking for? Full solutions? How far did you get?

On the 1/4 mile track: did you calculate that the semi-circles each have length of 345,
calculated this way : (5280/4 - 630) / 2 ?

Did you do some "searching", like Googling "inscribed circle of isosceles triangle" ?
• Jul 19th 2010, 03:31 PM
cutiemike1
Quote:

Originally Posted by Wilmer
What are you asking for? Full solutions? How far did you get?

On the 1/4 mile track: did you calculate that the semi-circles each have length of 345,
calculated this way : (5280/4 - 630) / 2 ?

Did you do some "searching", like Googling "inscribed circle of isosceles triangle" ?

#17..Where did you get this formula?? And how? I can't still figure it out.But I know that the race track which is equal to 1mile should be divide in order to get a quarter mile..

#19..I did some research and this is what i found out..

r = 2*(area of triangle) / (a+b+c)
= 2 * [0.5 * 4 * √(3^2 - (4/2)^2)] / (3+3+4)
= 2 * 2√5 / 10
= 2 / √5

Now my questions is..how did it come up with that kind of formula in "r".??

#21..It's hard.. I tried to use trigonometric functions.. T_T
• Jul 19th 2010, 04:21 PM
Wilmer
Quote:

Originally Posted by cutiemike1
....But I know that the race track which is equal to 1mile...

WHERE did you get 1 mile? Problem clearly states 1/4 mile.
• Jul 19th 2010, 04:26 PM
cutiemike1
oh yeah! i'm sorry...