TRIGONOMETRY

TRIGONOMETRY

1. (sinA)^2 +(cosA)^2 = 1

2. tanA = (sinA)/(cosA)

3. a/(sinA) = b/(sinB) = c/(sinC)

   • LAW OF SINES

4. a^2 = b^2 + c^2 - 2*b*c*cosA b^2 = a^2 + c^2 - 2*a*c*cosB c^2 = b^2 + a^2 - 2*b*a*cosC

   • LAW OF COSINES

5. SOLVING TRIANGLES

   • 1. Two sides and the angle between them
     • • Do 180º - 1st angle – 2nd angle to obtain the third one. • Law of sines to obtain sides.
   • 4. Three sides
     • Use law of cosines.
   • 2. Two sides and an angle not between them
     • • Law of cosines to obtain the third side. • Law of sines to find the smallest of the two angles (start with the shortest side) • Do 180º - 1st angle – 2nd angle to obtain the third one.
   • 3. Two angles and a side
     • • Law of sines to obtain the third side and angle. • Ambiguous case: there can be 0, 1 or 2 solutions. Must check all of them