Hi following a problem on a past exam and have come across a step i can't follow with the triangle inequality,
| 5x - y + (xy.cos(y))/(x^1/2 + y^1/2) |
is
<= 5|x| + |y| + |x|.|y|.|cos(y)|/(x^1/2 + y ^1/2)
and says it's via the trianlge inequality if someone can explain why it would be great cheers.