How do I figure out this question? Is there a formula I need?

Question

For which of the following sets of line segments is it possible to consturct a triangle?

1. Sides of length 17cm, 18 cm,and19 cm
2. Sides of length 11m, 18m, and 6 m
3. Sides of length 46ft, 25ft,and70ft

No side can be greater than the sum of the other two sides.

So that means none of these can construct a triangle then.

relook at 1. Is any side greater than the sum of the two others? What about 3?

1. no
2. yes
3. no

I am still kinda of confused on this.

Suppose you want to draw a triangle with sides 10, 3, and 5

first draw a base 10 cm long.
Now set a compass at 5 cm and and with its centre at the end of the line, draw an arc above the line.
Change the radius of your compass to 3 cm, set the centre of the compass at the end of the line and draw another arc above the line.

The intersection of these two arcs will be the third vertex of your triangle.
BUT in the case I gave you those two arcs never meet, so no triangle is possible

This shows the principle that "bobpursely" stated for you.

TO HAVE A TRIANGLE, THE SUM OF ANY OF THE TWO SIDES MUST BE GREATER THAN THE THIRD SIDE

Answer 1

measure and state the size of angle mn