Math Course, Quiz 14, question #1

Hello, I can’t get the right answer. I’ve double checked myself and checked WA/online calculators for angle and the answer is seems to be 167.1 deg. I’m confused, what am I missing here?

Hi @witwash.
In this question, the vectors have been normalized so you can use the formula θ = acos(a • b).
Since the answer is in degrees, you’ll also need to make sure that your calculator is in the right mode - no radians here!

If you could share the answer that you’re getting, along with your calculations, I’d be happy to point you in the right direction.

Here’s the full solution if you want check yours against the correct answer:

cosθ = a • b
cosθ = (0.4, 0.9) • (-0.6, -0.8)
cosθ = (0.4 * (-0.6) + 0.9 * (-0.8))
cosθ = (-0.96)
   θ = acos(-0.96)
   θ = 167.1°

I hope that helps but if you have any other questions please let me know.

Yeah, thank you. I forgot about normalized version and was confused.

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