Reflection: Complex Tasks Solving Trig Equations - Section 2: Share

 

When solving an equation like 4(sinx)^2 + 8sinx = -3, I was struck at how difficult trigonometric equations can be. This student's work is a great example of how students can get the correct answer with some minor misconceptions thrown in. I was really glad that the student was able to figure out that 330 degrees and 210 degrees would work. Many of my students were forgetting that a third quadrant angle would also give a sine value of -1/2.

However the student at one point wrote x = -3/2 and x = -1/2 instead of sinx = -3/2 and sinx = -1/2. I chose this student's work for our class discussion (my additions are in blue ink). Even through the student got the correct answer, the symbolism still caused some hiccups. I asked the class what the x stands for in this equation to reinforce the fact that it is an angle measure and that the sine of x gives us the ratios.

  Complex Tasks: The Complexity of Trigonometry
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Solving Trig Equations

Unit 5: Trigonometric Relationships
Lesson 9 of 15

Objective: SWBAT use factoring and the reciprocal properties to solve trigonometric equations.

Big Idea: Why do these trig equations have so many solutions?

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