If x = a sin b cos , y = a cos + b sin , then which of the following is true?

• A. <table><tr><td rowspan="2"></td><td rowspan="2"></td><td style="border-bottom:1px solid #000000;vertical-align:bottom;padding-bottom:2px;"><center>x </center></td><td rowspan="2">+<br></td><td style="border-bottom:1px solid #000000;vertical-align:bottom;padding-bottom:2px;"><center>a </center></td><td rowspan="2">= 1</td></tr><td align="center">y </td><td align="center">b </td></table>
• B. x + y = a b
• C. <table><tr><td rowspan="2"></td><td rowspan="2"></td><td style="border-bottom:1px solid #000000;vertical-align:bottom;padding-bottom:2px;"><center>x </center></td><td rowspan="2">+<br></td><td style="border-bottom:1px solid #000000;vertical-align:bottom;padding-bottom:2px;"><center>y </center></td><td rowspan="2">= 1</td></tr><td align="center">a </td><td align="center">b </td></table>
• D. x + y = a + b