how do you know when to use sin, cos, or tan on a graphing calc?

Question

or sin-1, cos-1, or tan-1?

Answer 1

since you are using these functions, I assume you know what sin, cos, tan are. Basically, you input an angle and you get a ratio (y/x, x/c, y/c).

sin-1 = arcsin, cos-1 = arccos etc.

This means that you put in a ratio, and it outputs an angle.

For example,

sin-1(1/2) = 30 degrees = arcsin(1/2)

With a graphing calculator, you have to watch out for the fact that most default to output in terms of radians. So if you get a strange number, check to see if you have it set to the right units (radians or degrees)

Answer 2

Okay, imagine the idk-what-it's-called-in-English-circle-w... which helps you with sin and cos. A negative cos (with which I mean the - sqrt(5/3)) means it should be in the 2nd or 4th quadrants (so on the left of the y-axis. A negative sin (with which I mean the -2/3) means it should be in the 3rd of 4th quadrants (so below the x-axis). Both must apply, so it's in the 4th quadrant. If you don't know that circle I'm talking about. Draw a circle with radius on. The center you call the origin O (0,0). The sin gives you the height and the cos gives you the width. We define that a theta = 0 (so 0 angle in degrees) means (1,0) (so 3 o'clock). Also, when theta = 90* (or pi/2) you're at (0,1) (so 12 o'clock). When you're at theta = 190* (or pi) you're at (-1,0) And theta = 270 would be (0,-1). So, the cos gives a negative number. In other words, the width is a negative number, so it's on the negative x-side. The sin gives a negative number. In other words, the height is a negative number, so it's on the negative y-side.

Answer 3

If you want to find the sine of an angle, use the sin button. When you want to know what angle has a particular sine value, use sin-1. Don't get confused thinking sin-1 = 1/sin - IT DOESN'T - it means the angle whose sine is . . . Same for cosine and tangent.

Answer 4

depending on which sides of the triangle you were given. e.g. sin /sin-1 if you were given the opposite side of the angle and the hypotenuse.

Answer 5

If you know one side and one angle, use sin (or whatever).

If you know two sides and not the angle, use arcsin (or whatever) to find the missing angle.