Bài 2: Tích vô hướng của hai vectơ

Bài 5 (trang 46 SGK Hình học 10): Trên mặt phẳng Oxy hãy tính góc giữa hai vectơ <svg style="display: inline-block; position: relative; top: -4px;" xmlns:xlink="http://www.w3.org/1999/xlink" width="2.324ex" height="3.009ex" viewBox="0 -1150.1 1000.5 1295.7" role="img" focusable="false" xmlns="http://www.w3.org/2000/svg" aria-labelledby="MathJax-SVG-1-Title"><title id="MathJax-SVG-1-Title">Equation</title><defs aria-hidden="true"><path stroke-width="1" id="E1-MJMATHI-61" d="M33 157Q33 258 109 349T280 441Q331 441 370 392Q386 422 416 422Q429 422 439 414T449 394Q449 381 412 234T374 68Q374 43 381 35T402 26Q411 27 422 35Q443 55 463 131Q469 151 473 152Q475 153 483 153H487Q506 153 506 144Q506 138 501 117T481 63T449 13Q436 0 417 -8Q409 -10 393 -10Q359 -10 336 5T306 36L300 51Q299 52 296 50Q294 48 292 46Q233 -10 172 -10Q117 -10 75 30T33 157ZM351 328Q351 334 346 350T323 385T277 405Q242 405 210 374T160 293Q131 214 119 129Q119 126 119 118T118 106Q118 61 136 44T179 26Q217 26 254 59T298 110Q300 114 325 217T351 328Z"></path><path stroke-width="1" id="E1-MJMAIN-20D7" d="M-123 694Q-123 702 -118 708T-103 714Q-93 714 -88 706T-80 687T-67 660T-40 633Q-29 626 -29 615Q-29 606 -36 600T-53 590T-83 571T-121 531Q-135 516 -143 516T-157 522T-163 536T-152 559T-129 584T-116 595H-287L-458 596Q-459 597 -461 599T-466 602T-469 607T-471 615Q-471 622 -458 635H-99Q-123 673 -123 694Z"></path><path stroke-width="1" id="E1-MJMAIN-2192" d="M56 237T56 250T70 270H835Q719 357 692 493Q692 494 692 496T691 499Q691 511 708 511H711Q720 511 723 510T729 506T732 497T735 481T743 456Q765 389 816 336T935 261Q944 258 944 250Q944 244 939 241T915 231T877 212Q836 186 806 152T761 85T740 35T732 4Q730 -6 727 -8T711 -11Q691 -11 691 0Q691 7 696 25Q728 151 835 230H70Q56 237 56 250Z"></path></defs><g stroke="currentColor" fill="currentColor" stroke-width="0" transform="matrix(1 0 0 -1 0 0)" aria-hidden="true"> <use xlink:href="#E1-MJMATHI-61" x="235" y="0"></use> <use xlink:href="#E1-MJMAIN-2192" x="0" y="561"></use></g></svg> và <svg style="display: inline-block; position: relative; top: -4px;" xmlns:xlink="http://www.w3.org/1999/xlink" width="2.324ex" height="3.676ex" viewBox="0 -1437.2 1000.5 1582.7" role="img" focusable="false" xmlns="http://www.w3.org/2000/svg" aria-labelledby="MathJax-SVG-1-Title"><title id="MathJax-SVG-1-Title">Equation</title><defs aria-hidden="true"><path stroke-width="1" id="E1-MJMATHI-62" d="M73 647Q73 657 77 670T89 683Q90 683 161 688T234 694Q246 694 246 685T212 542Q204 508 195 472T180 418L176 399Q176 396 182 402Q231 442 283 442Q345 442 383 396T422 280Q422 169 343 79T173 -11Q123 -11 82 27T40 150V159Q40 180 48 217T97 414Q147 611 147 623T109 637Q104 637 101 637H96Q86 637 83 637T76 640T73 647ZM336 325V331Q336 405 275 405Q258 405 240 397T207 376T181 352T163 330L157 322L136 236Q114 150 114 114Q114 66 138 42Q154 26 178 26Q211 26 245 58Q270 81 285 114T318 219Q336 291 336 325Z"></path><path stroke-width="1" id="E1-MJMAIN-20D7" d="M-123 694Q-123 702 -118 708T-103 714Q-93 714 -88 706T-80 687T-67 660T-40 633Q-29 626 -29 615Q-29 606 -36 600T-53 590T-83 571T-121 531Q-135 516 -143 516T-157 522T-163 536T-152 559T-129 584T-116 595H-287L-458 596Q-459 597 -461 599T-466 602T-469 607T-471 615Q-471 622 -458 635H-99Q-123 673 -123 694Z"></path><path stroke-width="1" id="E1-MJMAIN-2192" d="M56 237T56 250T70 270H835Q719 357 692 493Q692 494 692 496T691 499Q691 511 708 511H711Q720 511 723 510T729 506T732 497T735 481T743 456Q765 389 816 336T935 261Q944 258 944 250Q944 244 939 241T915 231T877 212Q836 186 806 152T761 85T740 35T732 4Q730 -6 727 -8T711 -11Q691 -11 691 0Q691 7 696 25Q728 151 835 230H70Q56 237 56 250Z"></path></defs><g stroke="currentColor" fill="currentColor" stroke-width="0" transform="matrix(1 0 0 -1 0 0)" aria-hidden="true"> <use xlink:href="#E1-MJMATHI-62" x="285" y="0"></use> <use xlink:href="#E1-MJMAIN-2192" x="0" y="814"></use></g></svg> trong các trường hợp sau:

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Xem thêm các bài giải bài tập Toán Hình học 10 Bài 2:

Giải bài 5 trang 46 sgk Hình học 10