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Two identical triangles can be combined into one () A. Parallelogram B. trapezoid C. rectangle
Because two identical triangles can form a parallelogram
How to judge that three line segments can form acute right angle and obtuse triangle
Primary school mathematics
Elementary school is impossible, junior high school can use Gougu theorem: A2 + B2 = C2 can be a right triangle
A2 + B2 larger than C2 can form an acute triangle (premise: ABC can encircle the triangle, and C is the largest)
How to judge right angle, acute angle, obtuse angle, triangle
Right angle, you can use a & sup2; + B & sup2;, see whether it is equal to C & sup2;, equal to right angle, other △ can be judged by trigonometric function, it depends on the specific topic
α. If β is the two acute angles of an acute triangle, then cos α
α. β is the two internal angles of an acute triangle, and the third internal angle must be less than 90 degrees
The total internal angle sum is 180 degrees,
Then there must be: α + β > 90, 90 > α > 90 - β > 0
sinα＞sin(90-β),sinα＞cosα,
f(sinα)＜f(cosβ),
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