When lines met or cross at a right angle are perpendicular lines.
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If the angle is larger than a right angle it is obtuse
An acute angle is smaller than a right angle.An obtuse angle is larger than a right angle.^_^
Use a protractor and they are classified as follows:- Acute angle: which is greater than 0 but less than 90 degrees Right angle: which is 90 degrees Obtuse angle: which is greater than 90 but less than 180 degrees Reflex angle: which is greater than 180 but less than 360 degrees
1. The side angle side theorem, when used for right triangles is often called the leg leg theorem. it says if two legs of a right triangle are congruent to two legs of another right triangle, then the triangles are congruent. Now if you want to think of it as SAS, just remember both angles are right angles so you need only look at the legs.2. The next is the The Leg-Acute Angle Theorem which states if a leg and an acute angle of one right triangle are congruent to the corresponding parts of another right triangle, the two right triangles are congruent. This is the same as angle side angle for a general triangle. Just use the right angle as one of the angles, the leg and then the acute angle.3. The Hypotenuse-Acute Angle Theorem is the third way to prove 2 right triangles are congruent. This one is equivalent to AAS or angle angle side. This theorem says if the hypotenuse and an acute angle of a right triangle are congruent to the hypotenuse and an acute angle of another right triangle, the two triangles are congruent. This is the same as AAS again since you can use the right angle as the second angle in AAS.4. Last, but not least is Hypotenuse-Leg Postulate. Since it is NOT based on any other rules, this is a postulate and not a theorem. HL says if the hypotenuse and a leg of one right triangle are congruent to the hypotenuse and a leg of another right triangle, then the triangles are congruent.
I generally use a pencil and ruler. To construct the right angle to draw it I also use compasses. To measure the right angle to draw it I also use a protractor.