SumDiffIdSE

Activity: Finding exact values Get the Gizmo ready: ● You should see the expression sin 75°. If not, click Refresh in your browser. The sum and difference identities you will use in this activity are given below: Sine Cosine sin ( α + β ) = sin α cos β + cos α sin β cos ( α + β ) = cos α cos β – sin α sin β sin ( α – β ) = sin α cos β – cos α sin β cos ( α – β ) = cos α cos β + sin α sin β 1. You should see the problem shown to the right at the top of the Gizmo. A. You are asked to use the Sine Angle Sum Identity. The first thing you need to do is write an expression for 75°. What must be true about this expression? 30+45=75 B. Choose the correct first step in the Gizmo. If your choice is incorrect, read the given feedback and try again. How did you rewrite sin 75°? sin(30+45) C. Choose the tile that shows the Sine Angle Sum Identity. Are the sine and cosine of these angles positive or negative? Positive D. Choose the last two correct steps. What does sin 75° equal? (root2+root6)/4 2. Click New . You should now see the problem shown at the right in the Gizmo. A. How can you rewrite –75° as a difference? 60-135 B. Choose the first two correct steps in the Gizmo. Are the sine and cosine of these angles positive or negative? Positive C. Choose the rest of the steps. What does cos (–75°) equal? (root6-root2)/4 3. Click New . Work through more problems in the Gizmo. Be sure to read the feedback. Reproduction for educational use only. Public sharing or posting prohibited. © 2020 ExploreLearning™ All rights reserved