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C2 Trigonometry identities

I need some help with trigonometry identities as I missed the lessons we had on them and I need to do some homework for it. Could someone please tell me how to do them with a walkthrough please(for just one question should be enough)? And the same for the proof question please. Thanks in advance

Section B: Solve each equation in the range 0° ≤ x ≤ 360°. Give answers correct to 1 decimal place.
13. 3−3cos𝑥=2sin^2𝑥
18. sin 2x = - ½
19. tan (2x+45) = 1.732

23. Prove the following identity:
(d) cos4𝜃−sin4𝜃≡cos2𝜃−sin2𝜃
Original post by kszyni1
I need some help with trigonometry identities as I missed the lessons we had on them and I need to do some homework for it. Could someone please tell me how to do them with a walkthrough please(for just one question should be enough)? And the same for the proof question please. Thanks in advance

Section B: Solve each equation in the range 0° ≤ x ≤ 360°. Give answers correct to 1 decimal place.
13. 3−3cos𝑥=2sin^2𝑥
18. sin 2x = - ½
19. tan (2x+45) = 1.732

23. Prove the following identity:
(d) cos4𝜃−sin4𝜃≡cos2𝜃−sin2𝜃


Do you know how to solve something like sin⁡(A)=12,0≤A≤360\sin(A)=\frac{1}{2}, 0\leq A \leq 360?? Because if you do not then you cannot really proceed onto these.
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kszyni1
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Yes I have solved those before


Posted from TSR Mobile
Original post by kszyni1
Yes I have solved those before


Posted from TSR Mobile


Then the others are straightforward though.

For the first one, use an identity which can turn sine squared into cosine squared then get a quadratic in terms of cosine and solve for it in the range.

For the second one, use substitution z=2x and solve for it that way. Then turn your final answers back to x.


Posted from TSR Mobile

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