Posted by **Aaron** on Saturday, April 4, 2009 at 3:58pm.

To find an angle where you have the opposite and adjacent which formula do you use? Sine, Cosine, Tan? and how do you find the inverse?

- Trig/Math -
**Reiny**, Saturday, April 4, 2009 at 5:04pm
as an example make a right-angled triangle ABC with AB=5, BC=4 and AC=3

(notice 3^2 + 4^2 = 5^2)

relative to angle B, AC is the opposite, and BC is the adjacent, and AB is the hypotenuse.

the ratio AB/BC = opposite/adjacent is called the tangent of an angle.

in this case tangent B = 3/4 = .75

to get angle B depends on your calculuator.

I have a "Sharp" in front of me, and there is a 2ndF key at the top left

so to get my angle I press

2ndF

tan

.75

=

and I get 36.87º

to get angle A, you simple take the difference between that angle and 90º, since angle C = 90

to find the tangent of the angle, press

tan

36.87

=

you should get very close to .75,

(we won't get .75 itself, since we rounded off our previous result)

google 'trig ratios' and you should get the other two definitions

also look up SOHCAHTOA

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