Cracking The SAT Premium

Summary

◦ Degrees   and angles:

• A circle contains 360 degrees.


• When you think about angles, remember circles.


• A line is a 180-degree angle.


• When two lines intersect, four angles are formed; the sum of their measures is 360 degrees.


• When two parallel lines are cut by a third line, the small angles are equal, the big angles are
  equal, and the sum of a big angle and a small angle is 180 degrees.

◦ Triangles:

• Every triangle contains 180 degrees.


• An isosceles triangle is one in which two of the sides are equal in length, and the two angles
  opposite the equal sides are equal in measure.


• An equilateral triangle is one in which all three sides are equal in length, and all three angles
  are equal in measure (60 degrees).


• The area of a triangle is bh.


• The height must form a right angle with the base.


• The Pythagorean Theorem states that in a right triangle, the square of the hypotenuse equals the
  sum of the squares of the two legs. Remember ETS’s favorite Pythagorean triplets (3-4-5 and
  5-12-13).


• Remember the other special right triangles: 45°-45°-90° and 30°-60°-90°.


• Similar triangles have the same angles and their lengths are in proportion.


• For trigonometry questions, remember SOHCAHTOA:
  
  
  • sin =
  
  
  • cos =
  
  
  • tan =
  
  
  
  

◦ Circles:

• The circumference of a circle is 2πr or πd, where r is the radius of the circle and d is the
  diameter.


• The area of a circle is πr2, where r is the radius of the circle.


• A tangent touches a circle at one point; any radius that touches that tangent forms a 90-degree
  angle.