You would start by finding the area of the circle and then finding the area of the rectangle. After finding both, subtract the area of the rectangle from that of the circle. <span />
1. It must be divisible by 2 and 3. It IS divisible by 2. it IS divisible by 3. No remainder.
2. Add the digits and see if the sum is divisible by 3. Apply this rule to both numbers. 3 is not a common factor.
3a. 639
3b. 1035
3c. 179
Sin 3pi/4 is angle 135 degrees or 45 degrees below 180 degrees. Hence it's opposite side is 1 and adjacent is 1, implying the hypothenus is sqrt(2). Hence
Sin 3pi/4 = 1/sqrt(2). Now multiply by sqrt(2)/sqrt(2) to get:
[1/sqrt(2).] * [sqrt(2)/sqrt(2)] = sqrt2)/2
