Math Identities

Math Identities

1. Pythagorean

   • sin^2(A)+cos^2(º)=1
   • 1+cot^2(º)=csc^2(º)
   • tan^2(º)+1=sec^2(º)

2. Reciprocal

   • csc=1/sin(º)
   • sec=1/cos(º)
   • cot=1/tan(º)

3. Even odd

   • sin(-(º))=-sin(º)
   • csc(-(º))=-csc(º)
   • cos(-(º))=cos(º)
   • sec(-(º))=sec(º)
   • tan(-(º))=-tan(º)
   • cot(-(º))=-cot(º)

4. Half angle

5. Double angle

   • sin(2(º))=
     • 2sin(º)cos(º)
   • cos(2(º))=
     • cos^2(º)-sin^2(º)
     • 1-2sin^2(º)
     • 2cos^2(º)-1
   • tan(2(º))
     • (2tan)/(1-tan^2(º)

6. Sum and difference

   • tan(a - b) = [tan(a) - tan(b)] / [1 + tan(a)tan(b)]
   • sin(α + β) = sin(α)cos(β) + cos(α)sin(β)
   • sin(α – β) = sin(α)cos(β) – cos(α)sin(β)
   • cos(α + β) = cos(α)cos(β) – s in(α)sin(β)
   • cos(α – β) = cos(α)cos(β) + sin(α)sin(β)
   • tan(a + b) = [tan(a) + tan(b)] / [1 - tan(a)tan(b)]

7. Quotient

   • cot(º)=cos(º)/sin(º)
   • tan=sin(º)/cos(º)

8. Problems

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