A Quick Review of Working with sine, cosine, tangent Topic Index | Algebra2/Trig Index | Regents Exam Prep Center

Let's start with a quick review of the three trigonometric functions we already understand.  Remember that these functions work only in right triangles.

 where A represents the angle of reference.

Example:
In right triangle ABC, hypotenuse length AB=15 and angle A=35º.    Find leg length BC to the nearest tenth.

Set up the problem:  Draw a right triangle.  Position yourself at the given angle as a point of reference.  Label the triangle's sides as to their location:  opposite, hypotenuse, adjacent.  Place the given information on the triangle.  Pair up the sides' labels with the given information.  The piece with no pairing is ignored.  Set up the function based upon the pairings and solve.

 Nothing is paired with side a in this problem, so it is ignored.  This problem deals with o and h which means we will be working with the sin function.

Example:
In right triangle ABC, leg length BC=15 and leg length AC=20.  Find angle A to the nearest degree.

Set up the problem:   The set up is the same as in the previous example.  The only difference is that in this problem you will be finding the angle.

 Nothing is paired with side h in this problem, so it is ignored.  This problem deals with o and a which means we will be working with the tan function.

Calculator use:  Remember you will need to activate the tan-1 key (it is located above the tan key) when finding angles.  To activate this tan-1 key on most scientific calculators, enter 0.75, press 2nd (or shift) and then the tan key.  On the graphing calculator, activate the tan-1 first, and then enter 0.75.