Cho tam giác ABC vuông tại A, có AB=AC, H là trung điểm của BC, M và N là hai điểm thuộc BC sao cho BM=CN

  1) CM:\(\Delta ABH=\Delta ACH\)từ đó tính các góc của tam giác ABC

  2) CM: \(\widehat{BAN}=\widehat{CAM}\)

  3) Qua A kẻ đường thẳng xy bất kì sao cho B, C nằm cùng phía đối với xy. Kẻ BD và CE cùng vuông góc với xy (D,E thuộc xy). 

      CM: DE=BD+CE

CMR<img src="data:image/gif;base64,R0lGODlhAQABAPABAP///wAAACH5BAEKAAAALAAAAAABAAEAAAICRAEAOw==" class="cke_reset cke_widget_mask"><span class="cke_reset cke_widget_drag_handler_container" style="background-attachment: initial; background-origin: initial; background-clip: initial; background-color: rgba(220, 220, 220, 0.496094); background-image: url(https://olm.vn/media/cke7/plugins/widget/images/handle.png); top: -15px; left: 0px; background-position: initial initial; background-repeat: initial initial; "><img class="cke_reset cke_widget_drag_handler" data-cke-widget-drag-handler="1" src="data:image/gif;base64,R0lGODlhAQABAPABAP///wAAACH5BAEKAAAALAAAAAABAAEAAAICRAEAOw==" width="15" title="Nhấp chuột và kéo để di chuyển" height="15" draggable="true">&gt;<span tabindex="-1" contenteditable="false" data-cke-widget-wrapper="1" data-cke-filter="off" class="cke_widget_wrapper cke_widget_inline" data-cke-display-name="toán" data-cke-widget-id="1"><span class="math-q cke_widget_element" style="display:inline-block;" data-cke-survive="1" data-cke-widget-keep-attr="0" data-widget="mathq" data-cke-widget-data="%7B%22math%22%3A%22%5C%5C(%5C%5Csqrt%7Ba%7D%5C%5C)%22%2C%22classes%22%3A%7B%22math-q%22%3A1%7D%7D"><iframe style="border-top-width: 0px; border-right-width: 0px; border-bottom-width: 0px; border-left-width: 0px; border-style: initial; border-color: initial; display: inline; vertical-align: middle; height: 31px; width: 52px; " scrolling="no" frameborder="0" allowtransparency="true" src="javascript:void(0)"><img src="data:image/gif;base64,R0lGODlhAQABAPABAP///wAAACH5BAEKAAAALAAAAAABAAEAAAICRAEAOw==" class="cke_reset cke_widget_mask"><span class="cke_reset cke_widget_drag_handler_container" style="background-attachment: initial; background-origin: initial; background-clip: initial; background-color: rgba(220, 220, 220, 0.496094); background-image: url(https://olm.vn/media/cke7/plugins/widget/images/handle.png); top: -15px; left: 0px; background-position: initial initial; background-repeat: initial initial; "><img class="cke_reset cke_widget_drag_handler" data-cke-widget-drag-handler="1" src="data:image/gif;base64,R0lGODlhAQABAPABAP///wAAACH5BAEKAAAALAAAAAABAAEAAAICRAEAOw==" width="15" title="Nhấp chuột và kéo để di chuyển" height="15" draggable="true">+<span tabindex="-1" contenteditable="false" data-cke-widget-wrapper="1" data-cke-filter="off" class="cke_widget_wrapper cke_widget_inline" data-cke-display-name="toán" data-cke-widget-id="2"><span class="math-q cke_widget_element" style="display:inline-block;" data-cke-survive="1" data-cke-widget-keep-attr="0" data-widget="mathq" data-cke-widget-data="%7B%22math%22%3A%22%5C%5C(%5C%5Csqrt%7Bb%7D%5C%5C)%22%2C%22classes%22%3A%7B%22math-q%22%3A1%7D%7D"><iframe style="border-top-width: 0px; border-right-width: 0px; border-bottom-width: 0px; border-left-width: 0px; border-style: initial; border-color: initial; display: inline; vertical-align: middle; height: 31px; width: 52px; " scrolling="no" frameborder="0" allowtransparency="true" src="javascript:void(0)"><img src="data:image/gif;base64,R0lGODlhAQABAPABAP///wAAACH5BAEKAAAALAAAAAABAAEAAAICRAEAOw==" class="cke_reset cke_widget_mask"><span class="cke_reset cke_widget_drag_handler_container" style="background-attachment: initial; background-origin: initial; background-clip: initial; background-color: rgba(220, 220, 220, 0.496094); background-image: url(https://olm.vn/media/cke7/plugins/widget/images/handle.png); top: -15px; left: 0px; background-position: initial initial; background-repeat: initial initial; "><img class="cke_reset cke_widget_drag_handler" data-cke-widget-drag-handler="1" src="data:image/gif;base64,R0lGODlhAQABAPABAP///wAAACH5BAEKAAAALAAAAAABAAEAAAICRAEAOw==" width="15" title="Nhấp chuột và kéo để di chuyển" height="15" draggable="true"><br></p><p><p><s>va,b=+<br></p>

Bài 2: Cho hình vẽ

 

A) Chứng minh   \(\Delta ABH=\Delta ACH\)

B) Chứng minh \(AH\perp BC\)

C) Chứng minh AH là tia phân giác của <BAC