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Let sin 22° = p. Determine the following ratios in terms of p: 2.2.1 sin 202°, 2.2.2 cos 44°

Mathematics

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Step-by-step solution

4 steps

Given sin⁡22∘=p\sin 22^\circ = p.

2.2.1

  1. Express sin⁡202∘\sin 202^\circ in terms of a reference angle.

    The angle 202∘202^\circ lies in the third quadrant. The reference angle is 202∘−180∘=22∘202^\circ - 180^\circ = 22^\circ.
    In the third quadrant, the sine function is negative.

    sin⁡202∘=sin⁡(180∘+22∘)=−sin⁡22∘\sin 202^\circ = \sin (180^\circ + 22^\circ) = -\sin 22^\circ
  2. Substitute the given value of sin⁡22∘\sin 22^\circ.

    Since sin⁡22∘=p\sin 22^\circ = p, we have:

    sin⁡202∘=−p\sin 202^\circ = -p

    The final answer is −p\boxed{\boldsymbol{-p}}.

    2.2.2

  3. Express cos⁡44∘\cos 44^\circ using a double angle identity.

    We know that 44∘=2×22∘44^\circ = 2 \times 22^\circ. We can use the double angle identity for cosine, cos⁡2θ=1−2sin⁡2θ\cos 2\theta = 1 - 2\sin^2 \theta.
    Let θ=22∘\theta = 22^\circ.

    cos⁡44∘=cos⁡(2×22∘)=1−2sin⁡222∘\cos 44^\circ = \cos (2 \times 22^\circ) = 1 - 2\sin^2 22^\circ
  4. Substitute the given value of sin⁡22∘\sin 22^\circ.

    Since sin⁡22∘=p\sin 22^\circ = p, we have:

    cos⁡44∘=1−2(p)2=1−2p2\cos 44^\circ = 1 - 2(p)^2 = 1 - 2p^2

    The final answer is 1−2p2\boxed{\boldsymbol{1 - 2p^2}}.

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