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Old 07-27-2007   #1
piiiowfort
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Default stuck on only these "easy" geometry questions?

i finished all the other problems but i couldnt figure out how to do these, even by reading the chapter over and over. please show me HOW you got these:1. If x and 3x - 10 represent the measure of the acute angles of a right triangle, find the value of x. show all work.2. A regular polygon has 12 sides. Find the measure of each exterior angle. show all work.3. Four of the angles of a pentagon have measures 30, 70, 120 and 165. Find the measure of the fifth angle. show all work.
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Old 07-27-2007   #2
Star
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I am not sure what is acute angles but if they are the other two angles of the right-angled triangle, then it would be easy to solve.firstly, a triangle has a total of 180 degrees so,180 dregree - 90 degree = 90 degree( right angle = 90 degree)x + ( 3x - 10) = 90 degreee.therefore x + 3x - 10 = 90 degreeadd up x :4x - 10 = 90plus 10 on both sides :4x - 10 + 10 = 90 + 104x = 100x = 25hope i am correct
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Old 07-27-2007   #3
johngalt4273
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1. not sure - try http://mathforum.org/library/problem..._rttris.html2. Finding the sum of the exterior angles of a polygon is simple. No matter what type of polygon we have, the sum of the exterior angles is ALWAYS equal to 360ºDivide 360 by 12 (assuming they are equal angles). 3. it does not specify interior or exterior, but i assume they mean interior.to find interior angles of a polygonsum of angles = (n – 2)180°n = total number of sides... that's 5(5 - 2) x 180 = 54030+70+120+165 = 385540 - 385 = 155
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Old 07-27-2007   #4
army_ranger
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1)x+3x-10+90=180, since the sum of all the angles of a triangle is 180 degrees. a)4x+80=180 b)4x=100 c)x=252)easy, sum of ex. anlges is 360/n(n is number of sides) a)360/12= 303)sum of in. angles of pentagon is 540 degrees, 30+70+120+165+x=540100+285+x=540385+x=540x=155
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Old 07-27-2007   #5
Alvin P
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1. A right triangle has a right angle, therefore there are only 90 degrees left in the triangle. so:3x-10+x=90 4x=100 x=25 other angle=-3x-10 3 times 25=75 75-10= 652. All the exterior angles added up equals 360. So....360/12=303. To find the total number of all angles in a polygon, it is # of angles minus 2 times 180(Number-2)180so(5-2)1803*180=54030+70+120+165=385540-385= 155
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Old 07-27-2007   #6
calmserene
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sum of the 2 acute angles of a rt triangle =90 degreesso, x+3x-10=904x=100x =25
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