# Math

More Options: Make a Folding Card

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• Meet James! He is a Grade 11 student that is in MC3U1 course. He just got back his trigonometry test and is confused on how he failed.
• I can't believe I failed this test. My mom is going to kill me. I need to go get help, so I don't make this mistake on my exam!
• Hey buddy, are you okay?
• As James was boarding the subway, he suddenly met a woman who noticed that he was upset.
• No, I am not okay, I just failed my trigonometry test, and my mom is going to kill me.
• It looks like you got question 1 wrong. Can you explain to me what you did?
• I don't know how I got it wrong. I swear I did everything properly!
• Sin x=1/3 19.5 180-19.5 =160.5
•  Solve the equation 6cos2 x-sinx-5=0, for the
• interval between 0 and 360 degrees.
• Therefore, the answer is 19.5*, 160.5*, 30*, 210*
•  6cos2x-sinx-5=0 6cos2x-1-cosx-5=0
• 6cos2x-cosx-5=0 (-3a+1)(2a+1)=0
• Trigonometry Test
• Sinx=-1/2 30 180+30 =210
• James
• Oh, I see where you made a mistake. First of all, you misused a trigonometry identity when you were simplifying Sinx in your equation.
• I don't understand, isn't Sinx=1-Cosx a trigonometric identity?
• No, this is a very common mistake. You mistook Sinx for Sinx2. You cannot change Sinx to 1-Cosx because it is not a trigonometry identity.
• Oh ya! So in this equation, I will change Cos2x to 1-Sin2x instead.
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