Question

Please help me out ?

Answer 1

An obtuse triangle is formed if there is an angle that has a measure of more than 90 degrees. You can determine if an obtuse angle is formed by two sides of a triangle if it meet this condition:

Let a and b be two sides of a triangle and c is the longest side:
$a^{2} + b^{2} \ \textless \ c^{2}$

So taking your given:

$10^{2} + 15 ^{2}$ < $c^{2}$
100 + 225   < $c^{2}$
325  <  $c^{2}$

To get the smallest possible number, just get the square root of both sides:

$\sqrt{325}$ < $\sqrt{c^{2} }$
  18.03  < c

So your smallest possible whole number is 19