+302 Prove that the points (2,-2), (-2,1) and (5,2) are the vertices of a right-angled triangle. Also, find the area of the triangle.
+312 Find the lengths of the triangle's edges and use the pythagoras theorem. Good luck.
+302 yes. i got the answer. but when i first attempted the question i changed the co-ordinates of the vertices. if the co-ordinates are changed we don't get a right answer right? The first one is mine and the 2ed one is alan's.
+312 no, we WILL get a right triangle. You simply wrote 'B' instead of 'A', 'C' instead of 'B' and 'A' instead of C. it doesnt change the fact its a right triangle. well yes, in alans picture the angle b=90. in your inaccurate picture (which is probably the reason you got confused) c=90.
its like calling x 'n' in x*2+3=5 and thinking the answer will be different. it wont. you didnt change anything besides the letters and it doesnt matter. dont worry, you got the right answer.
+302 But in my dig angle b=90. my co-ordinated were in the wrong places so my answer was wrong.
my working was like this: (as per the 1st dig)
AB=\(\sqrt{}25 = 5\)
BC =\(\sqrt{}50 =5\sqrt{}2\)
AC= \(\sqrt{}25 = 5\)
using pythagoram theorm, AC²=AB²+BC²
5=5²+\(5\sqrt{}2\)²
5 not = 25+50
But as per Alan's dig:
AB=\(\sqrt{}25 = 5\)
BC =\(\sqrt{}25 = 5\)
AC=\(\sqrt{}50 =5\sqrt{}2\)
using pythagoram theorm, AC²=AB²+BC²
\(5\sqrt{}2\)²=5²+5²
50=25+25=50
+312 Ok i think i know how to explain it to you.
when you first learned the pythagoras theorem, the teacher probably drew a right triangle on the board. The teacher then marked the right angle with the letter 'B' and said that (AB)2+(BC)2=(AC)2.
The teacher was right. But you forgot something. You dont have to mark the right angle with 'B'. The teacher coulve marked it with 'C'. That means instead of (AB)2+(BC)2=(AC)2 the theorem would've been (BC)2+(AC)2=(AB)2. You dont need to mark something with a specific letter for it to work.
what you did wrong is you marked a specific angle with B and thought it means B is the right angle! but thats wrong, because 'A' is the right angle!.
also, in my first post i wrote:
You simply wrote 'B' instead of 'A', 'C' instead of 'B' and 'A' instead of 'C'.
I was wrong, i dont know if it helps you but you wrote 'A' instead of 'B', 'B' instead of 'C' and 'C' instead of 'A'.
hope it helps!
+302 yes i know that. the letters can be changed but i did'nt understand by what u meant as
"what you did wrong is you marked a specific angle with B and thought it means B is the right angle! but thats wrong, because 'A' is the right angle!."
but B is the right angle ryt?
