Write out the sum formula for sin <span>sin(x + y) = sinxcos + sinycosx </span>
<span>Then expand sin(a + b) + sin(a - b) </span> <span>sinacosb + sinbcosa + sinacosb - sinbcosa </span> <span>The 2nd and 4th terms cancel and you get </span> <span>2sinacosb</span>
<h3>Step-by-step explanation: for #2, look at 6 3/4 and make it into a decimal. Do the same to 7 1/2. Compare them both to see which one is shorter by subtracting 6 3/4 from 7 1/2 and when you get your answer for that, make that into a fraction. Predict that 6 3/4 is shorter because of how much less it is compared to 7 1/2. (I hope I helped you in some way. Good luck!)</h3>
