Lesson 9: Using Trigonometry to Find Missing Angles

                                       Module 1 Part 2: Trigonometry                                            

This activity will explore how to use your calculator to find missing angles given a trig ratio.

1. Find <A given the trig statement sin A = 0.5.
To do this we need to access the inverse sin function (shown on your calculator as sin^-1). This function helps us find what angle gives us a sin of 0.5.  Look on your calculator and locate sin^-1. It will be above the sin button.
The calculator button sequence used to find <A is
     0.5    

Your calculator screen will look like this:

Therefore, <A = 30^o.

2. Find the measure of <D when cos D = 0.7071
The calculator button sequence is very similar to above except we use cos^-1.
     0.7071     

Your calculator screen will look like this:

Therefore, <D = 45^o.

3. Find the measure of <G given tan G = ¼

The calculator button sequence is very similar to above except we use tan^-1 and we have to enter the fraction ¼.

        1   ÷    4        

Your calculator screen will look like this:

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Tip

The button on our calculator helps us to find missing angles.

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