 Thread starter
 #1
Please refer to the diagram.
I am asked to find cos  180^{0 }and sin 180^{0 }by plotting a point p on a circle.
OK I don't understand the following before I begin to answer.
How do I know where to start to draw the circles?
I have the x and y axis. I know that anticlockwise rotation is positive and clockwise is negative.
If I look first at cos  180^{0 }I know I am going to draw a semi circle in the clockwise direction, which will represent 180^{0 }but show as  180^{0 }on the diagram.
I am confused how I draw the sin 180^{0 }and am assuming that I draw the semi circle in a anticlockwise direction labelled also  180^{0 }to end up with a circle.
I also don't understand from a drawing how I am supposed to know that cos  180^{0 }=  1, and sin  180^{0 }= 0
From first principles and not looking at the calculator, how would I know that these values are right, I could have drawn the semicircles from x = 2 or 3 etc?
Please advise if you can.
Kind regards
Casio
I am asked to find cos  180^{0 }and sin 180^{0 }by plotting a point p on a circle.
OK I don't understand the following before I begin to answer.
How do I know where to start to draw the circles?
I have the x and y axis. I know that anticlockwise rotation is positive and clockwise is negative.
If I look first at cos  180^{0 }I know I am going to draw a semi circle in the clockwise direction, which will represent 180^{0 }but show as  180^{0 }on the diagram.
I am confused how I draw the sin 180^{0 }and am assuming that I draw the semi circle in a anticlockwise direction labelled also  180^{0 }to end up with a circle.
I also don't understand from a drawing how I am supposed to know that cos  180^{0 }=  1, and sin  180^{0 }= 0
From first principles and not looking at the calculator, how would I know that these values are right, I could have drawn the semicircles from x = 2 or 3 etc?
Please advise if you can.
Kind regards
Casio
Attachments

14.4 KB Views: 7