The side lengths of a triangle are 15.8 cm, 7.9 cm and 22.3 cm. find the perimeter of the triangle.

No, Lydia's assertion is not correct

Step-by-step explanation:

Plot three Lydia's points D(-2, -1) , E (-2, 2), and F (0, 0) on the coordinate plane (see attached diagram).

Triangle DEF will be right triangle if one of its angle is right angle. If one angle is right angle, then adjacent sides are prependicular. If two sides are perpendicular, then the dot product is equal to 0.

1. Dot product between vectors DE and DF:

So, DE and DF are not perpendicular, and angle D is not right angle.

2.  Dot product between vectors ED and EF:

So, ED and EF are not perpendicular, and angle E is not right angle.

3. Dot product between vectors FD and FE:

So, FD and FE are not perpendicular, and angle F is not right angle.