Where did I go wrong?

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Trigonometry

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Question: https://imgur.com/t8vsOZm

Double Angle Formula: https://imgur.com/7pPZOSB

Answer: https://imgur.com/ZaTTi96

My Answer: https://imgur.com/csjyIZd

Heyy, can someone tell me where I went wrong here?

Basically, I did the question in a different way compared to the video, and I got different answers (different reference angle) compared to the video.

I used the double angle formulas (as shown in the image above), and you can basically see with the image in how I arrived with my answer. Did I use the double angle formula incorrectly, or did I cancel it wrong? This is new to me so please help correct my mistakes, thanksss.

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Posted: 4 months ago
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