Question 1203040
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In a right triangle with the standard notation with c being the length of the longest side (hypotenuse), the relationship {{{c^2=a^2+b^2}}} holds.<br>
For a triangle to be obtuse, again using c to denote the length of the longest side, the relationship {{{c^2>a^2+b^2}}} must hold.<br>
In this problem, there are two cases to consider -- the longest side can be either k or 15.<br>
(1) k is the longest side<br>
The triangle inequality tells us that k<11+15=26.<br>
For the triangle to be obtuse, we need to have<br>
{{{k^2>11^2+15^2}}}
{{{k^2>346}}}
{{{k>18.6}}} approximately<br>
The integers greater than 18.6 and less than 26 are 19 through 25 inclusive -- that's 7 possible integer values for k.<br>
(2) 15 is the longest side<br>
Now the triangle inequality tells us k>15-11=4.<br>
For the triangle to be obtuse, we need to have<br>
{{{15^2>k^2+11^2}}}
{{{225-121>k^2}}}
{{{k^2<104}}}
{{{k<10.2}}} approximately<br>
The integers greater than 4 and less than 10.2 are 5 through 10 inclusive -- that's 6 possible integer values for k.<br>
ANSWER: 7+6 = 13<br>