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The formula of cosine theorem
A, B, C are the three sides of a triangle, and a B C is the diagonal of the three sides
cosA=(b^2+c^2-a^2)/2bc
cosB=(a^2+c^2-b^2)/2ac
cosC=(a^2+b^2-c^2)/2ab
What is the relationship between the three sides of an obtuse triangle? What theorem?
According to the cosine theorem, if the triangle is an obtuse angle triangle and the longest side length is C, then C ^ 2 > A ^ 2 + B ^ 2 is satisfied
On the contrary, if C ^ 2 > A ^ 2 + B ^ 2, the angle c is an obtuse angle, and the triangle is an obtuse angle triangle
Using sine cosine theorem to find triangle area
Triangle area = 1 / 2absinc = 1 / 2acsinb = 1 / 2bcina
How to draw the three heights of an obtuse triangle? Be careful!
Make an extension line on both sides of the obtuse angle, and then make a high line
How to draw the height of an obtuse triangle?
Lengthen one side of the obtuse triangle and make a height on this edge
How to draw the height of an obtuse triangle There must be no picture of high reward
That's it
How to draw the height of an obtuse triangle? Is it outside the triangle?
Yes, it's on the outside. Just extend it
How to draw the height of an obtuse triangle?
Make an extension line at the bottom edge, and make a vertical line down the fixed point to intersect
How to draw three heights of acute triangle, right triangle and obtuse triangle
Acute angle: make a vertical line from a vertex of a triangle to its opposite side. The line segment between the perpendicular feet of the vertex is the height of the triangle
Right angle: it is the right angle side. The other way is the same as above
Obtuse angle: make a vertical line from a vertex of a triangle to its opposite side. The line segment between the perpendicular feet of the vertex is the height of the triangle, but there are two opposite sides that need to be extended
OK, that's it
Draw the inscribed circles of the known acute angle triangle, right angle triangle and obtuse angle triangle respectively, and observe whether the heart of the triangle is in the triangle
As shown in the figure:
The heart is in the triangle
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