3.若α为锐角,且sinα+cosα=$\frac{5}{4}$,则sinα•cosα的值为( )
| A. | $\frac{5}{32}$ | B. | $\frac{7}{32}$ | C. | $\frac{9}{32}$ | D. | $\frac{11}{32}$ |
1.若代数式$\frac{{4-{x^2}}}{{\sqrt{1+x}}}$的值等于零,则x的值等于( )
0 286369 286377 286383 286387 286393 286395 286399 286405 286407 286413 286419 286423 286425 286429 286435 286437 286443 286447 286449 286453 286455 286459 286461 286463 286464 286465 286467 286468 286469 286471 286473 286477 286479 286483 286485 286489 286495 286497 286503 286507 286509 286513 286519 286525 286527 286533 286537 286539 286545 286549 286555 286563 366461
| A. | ±2 | B. | 2 | C. | -2 | D. | ±4 |