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how do you find the sign of a given point

Guest Apr 20, 2017
#1
+556
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to find the sign of a number, you divide that number by its absolute value. If the number is 0, the sign is 0.

If you want to find the sine of an angle, you can draw a circle with radius 1. Then, starting at the top, go that many units around the circle. The x value is the sine, the y value is the cosine, and the x value divided by the y value is the tangent.

helperid1839321  Apr 20, 2017
#2
+7324
+3

Hey! Are you really just in 8th grade?

To find the sin of the angle that a line from the origin to a specific point makes with the x-axis...a point like this (4, 7) :

1. Find the distance from the point to the origin. This is the radius.

2. Divide the y coordinate, in this case 7, by that distance.

Dividing by the radius scales the length down to unit circle measures.

For this one, use the Pythagorean theorem or distance formula (same thing really) to find that the radius = $$\sqrt{65}$$

And the sine of the angle that a line from the origin to this point makes with the x-axis = $$\frac{7}{\sqrt{65}}$$

If the radius is already = 1, then just get the y-coordinate of the point! :)

Also... to find the sin if an angle is given, exactly what you said works but I think you want to start at the right-most point on the circle. On a clock, that's 3:00. In a unit circle, that is the point (1, 0). Then go counter-clockwise.

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hectictar  Apr 22, 2017