.
The wording is specially intended to confuse a reader.
Normal wording should say
There are three points in a coordinate plane,
A at ((0,0), B at (1,0) and C at (1,1).
Find the area of triangle ABC.
S O L U T I O N
Triangle ABC is a right angled triangle.
It has horizontal leg AB of the length 1 and vertical leg BC of the length 1.
Triangle ABC is a right angled triangle.
Its area is half-product of its legs = = square units. ANSWER
Solved.
In the form how the problem is worded and presented in the post,
is is not a mathematical style of writing.