- GRAPHING HORIZONTAL AND VERTICAL LINES.
OUR GOAL IS TO GRAPH LINES IN THE FORM OF Y = C AND X = A,
WHERE C AND A ARE SOME CONSTANTS.
IT'S PRETTY STRAIGHTFORWARD, SO LET'S JUMP INTO IT.
WE WANT TO GRAPH Y = -2.
WELL, THIS GRAPH WOULD CONSIST OF ALL THE ORDERED PAIRS
WHOSE Y COORDINATE IS -2.
LET'S JUST SAY FOR EXAMPLE,
WE WEREN'T SURE HOW TO GRAPH THIS
AND WE WANTED TO KIND OF DO SOME VERIFICATION OF OUR OWN.
WE ALWAYS GO BACK TO THE STANDARD T-TABLE.
NOW, IF YOU TAKE A LOOK AT THIS EQUATION, Y = -2.
THERE'S NO QUESTIONS ABOUT THAT, Y HAS TO BE -2.
HOWEVER, THERE ARE NO CONDITIONS BASED UPON THE VARIABLE X,
SO, THEREFORE, X COULD BE ANYTHING.
I'LL JUST GO AHEAD AND MAKE IT (0,1,2).
IF I WAS TO PLOT THESE THREE POINTS,
YOU COULD QUICKLY SEE THAT IS GOING TO BE A HORIZONTAL LINE.
AND, IN FACT, THAT'S EXACTLY WHAT IT IS.
HORIZONTAL LINE THROUGH Y = -2.
NOW, THIS IS A FUNCTION. REMEMBER THE FUNCTION TEST
IS DOES PASS THE VERTICAL LINE TEST.
AND IT IS NOT POSSIBLE TO DRAW
A VERTICAL LINE ACROSS THIS GRAPH IN MORE THAN ONE POINT,
SO, YES, IT IS A FUNCTION.
AND, IN FACT, EVERY HORIZONTAL LINE WILL BE A FUNCTION.
THE OTHER CASE, WHAT IF WE HAVE A LINE IN THE FORM OF X = 3.
WELL, THIS GRAPH CONSIST OF ALL THE ORDERED PAIRS
WHO'S X COORDINATE IS 3.
AGAIN, IF I REALLY WANTED TO MAKE A T-TABLE FOR THIS,
I COULD.
THE CONDITION FOR THIS T-TABLE IS THE X HAS TO BE EQUAL TO 3.
AGAIN, THERE ARE NO CONDITIONS FOR THE Y COORDINATE
GIVEN IN THE EQUATION, Y CAN BE ANY VALUE.
I'LL MAKE IT STRAIGHT FORWARD AND EASY TO GRAPH.
GRAPH THESE THREE POINTS,
THEN WE SHOULD HAVE OUR LINE, (3,0), (3,1), (3,2).
OKAY, OUR VERTICAL LINE LOOKS JUST LIKE THAT.
AND THE QUESTION IS, IS THIS A FUNCTION,
AND, IN FACT, IT'S NOT A FUNCTION
BECAUSE THERE'S ONLY ONE VERTICAL LINE
THAT WOULD INTERSECT THIS GRAPH, AND THAT WOULD BE ITSELF.
AND IT WOULD OBVIOUSLY BE CROSSING THE LINE
IN MORE THAN ONE POINT,
SO IT'S NOT FUNCTION.
NO VERTICAL LINE WILL BE A FUNCTION.
THAT'S PRETTY MUCH IT FOR HORIZONTAL AND VERTICAL LINES.
LET'S SEE HOW WE GRAPH THESE ON THE GRAPHING CALCULATOR.
TO GRAPH HORIZONTAL LINES, IT'S VERY STRAIGHT FORWARD,
YOU PRESS Y = THE VERY TOP LEFT, TYPE IN YOUR FUNCTION.
FOR EXAMPLE, WE GRAPHED Y = 2,
HIT GRAPH AND YOU HAVE A NICE HORIZONTAL LINE.
HOWEVER, WHEN YOU'RE IN THE MENU Y EQUALS,
NOTICE THERE'S NO ROOM FOR X EQUALS.
SO THERE'S A SPECIAL FUNCTION JUST TO GRAPH VERTICAL LINES.
IF YOU GO BACK TO THE HOME SCREEN, SECOND QUIT.
AND YOU HIT THE DRAW MENU, WHICH IS SECOND PROGRAM.
OPTION 4 WILL GRAPH A VERTICAL LINE, HIT OPTION 4.
AND WE GRAPHED, I BELIEVE IT WAS X = 3.
SO IF I TYPE IN JUST THE NUMBER 3, AND THEN HIT ENTER.
IT WILL GRAPH A VERTICAL LINE.
ONE WORD OF CAUTION,
IN ORDER TO CLEAR THIS GRAPH FROM THE SCREEN,
YOU DO HAVE TO GO BACK IN TO SECOND PROGRAM
AND HIT OPTION 1 TO CLEAR THE GRAPH.
OTHERWISE, IT'LL KEEP GRAPHING THAT VERTICAL LINE.
OF COURSE TO CLEAR THE HORIZONTAL LINE,
YOU HAVE TO JUST CLEAR OUT THE EQUATION THAT WE'VE ENTERED,
AND IT WILL ALSO BE GONE.