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Without using tables or calculator, evaluate: sin 45 - cos 60 / sin 10 + sin 50 / 2 cos 40 (b) The minute hand of a clock moves from 1:15 to 5:45 in the face of the clock. If the length of the minute hand is 7cm, find correct to three significant figures, the area swept by the minute hand [Take pi = 22/7]

Mathematics

ScanSolve AI Answer

Answer

2−12\frac{\sqrt{2} - 1}{2}

Step-by-step solution

5 steps
  1. Evaluate sin⁡45∘\sin 45^\circ.

    We know that sin⁡45∘=22\sin 45^\circ = \frac{\sqrt{2}}{2}.

  2. Simplify the term cos⁡80∘sin⁡10∘\frac{\cos 80^\circ}{\sin 10^\circ}.

    Using the complementary angle identity cos⁡θ=sin⁡(90∘−θ)\cos \theta = \sin (90^\circ - \theta), we have:

    cos⁡80∘=sin⁡(90∘−80∘)=sin⁡10∘\cos 80^\circ = \sin (90^\circ - 80^\circ) = \sin 10^\circ

    Substitute this into the expression:

    cos⁡80∘sin⁡10∘=sin⁡10∘sin⁡10∘=1\frac{\cos 80^\circ}{\sin 10^\circ} = \frac{\sin 10^\circ}{\sin 10^\circ} = 1
  3. Simplify the term sin⁡50∘2cos⁡40∘\frac{\sin 50^\circ}{2 \cos 40^\circ}.

    Using the complementary angle identity sin⁡θ=cos⁡(90∘−θ)\sin \theta = \cos (90^\circ - \theta), we have:

    sin⁡50∘=cos⁡(90∘−50∘)=cos⁡40∘\sin 50^\circ = \cos (90^\circ - 50^\circ) = \cos 40^\circ

    Substitute this into the expression:

    sin⁡50∘2cos⁡40∘=cos⁡40∘2cos⁡40∘=12\frac{\sin 50^\circ}{2 \cos 40^\circ} = \frac{\cos 40^\circ}{2 \cos 40^\circ} = \frac{1}{2}
  4. Combine the simplified terms.

    Substitute the values from Step 1, Step 2, and Step 3 into the original expression:

    sin⁡45∘−cos⁡80∘sin⁡10∘+sin⁡50∘2cos⁡40∘=22−1+12\sin 45^\circ - \frac{\cos 80^\circ}{\sin 10^\circ} + \frac{\sin 50^\circ}{2 \cos 40^\circ} = \frac{\sqrt{2}}{2} - 1 + \frac{1}{2}
  5. Perform the arithmetic.

    22−1+12=22−22+12=2−2+12=2−12\frac{\sqrt{2}}{2} - 1 + \frac{1}{2} = \frac{\sqrt{2}}{2} - \frac{2}{2} + \frac{1}{2} = \frac{\sqrt{2} - 2 + 1}{2} = \frac{\sqrt{2} - 1}{2}

    The final answer is 2−12\frac{\sqrt{2} - 1}{2}.

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