An acute angle is a angle less than 90 degrees
here's three <>^
To prove that two right triangles are similar, all you need to show is that one of them has one acute angle that's equal to one acute angle of the other one.
That's exactly what the box means! That box is there to show that an angle is right, as right angles can have different properties than acute or obtuse angles.
Every minute on a round clock is six degrees. Putting the hands on 12 and 3 (15 minutes) would be a 90 degree angle.
At 3 hours 45 minutes there is not an acute angle between the hands of the clock (unless you extend the hands backwards).
An acute angle is a angle less than 90 degrees
here's three <>^
1) 190 2) 150 3) 16 2/3 4) 931/2
It's at 300o and it shows it's ten o'clock
To prove that two right triangles are similar, all you need to show is that one of them has one acute angle that's equal to one acute angle of the other one.
Two acute angles and two obtuse angles. If you do not know what these angles are, I will show you. An acute angle is an angle that has less than 90 degrees on your protractor (Shaped like a semi-circle. Found in a mathematical set). An obtuse angle has more than ninety degrees. An angle with ninety degrees is a right angle.
I can't show you the exact image but it will be 90/3= 30 degrees which is also an acute angle.
That's exactly what the box means! That box is there to show that an angle is right, as right angles can have different properties than acute or obtuse angles.
Two lines that form a right angle are Perpendicular. This can be show by an upside down T.
Think of your regular trapezoid (half a hexagon). Now cut it in half with a line perpendicular to the top and bottom. You can see the right angles along one side. The top and bottom lines are parallel. The seond angle on the bottom is acute, and the second top is obtuse. Can't be bothered to provide diagrams, though. Draw them yourself.
Since a right triangle has 180 degree angles in it, you know 2 angles already. One is the 90 degree angle, since the triangle is a right one. The other is 40 degrees, as in your statement. 90 plus 40 is 130. 50 degrees is the missing angle since 50 + 40+ 90 equal 180 degrees. Hopefully that helped you.