Angles and Triangles Basics

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Questions and Answers

If angle A and angle B are complementary, and sin(A) = 1/2, what is cos(B)?

  • 1
  • √2/2
  • √3/2 (correct)
  • 1/2

Which of the following is NOT a trigonometric identity?

  • tan(A) = sin(A)/cos(A)
  • sin²(A) + cos²(A) = 1
  • cos(2A) = cos²(A) + sin²(A) (correct)
  • sin(A + B) = sin(A)cos(B) + cos(A)sin(B)

In a right triangle, the length of the hypotenuse is 10 and the length of one leg is 6. What is the sine of the angle opposite the leg of length 6?

  • 3/5 (correct)
  • 4/5
  • 4/3
  • 3/4

What is the value of tan(45°)?

<p>1 (B)</p> Signup and view all the answers

What is the value of cos(120°)?

<p>-1/2 (B)</p> Signup and view all the answers

If sin(A) = 3/5 and cos(A) = 4/5, what is the value of tan(A)?

<p>3/4 (D)</p> Signup and view all the answers

If sin(A) = 1/3, what is the value of cos(2A)?

<p>-8/9 (C)</p> Signup and view all the answers

What is the value of sin(180° - A) in terms of sin(A)?

<p>sin(A) (B)</p> Signup and view all the answers

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Study Notes

Angles and Triangles

  • Degrees and Radians: Angles can be measured in degrees or radians. 1 radian is equivalent to 180/Ï€ degrees.
  • Angle Properties:
    • Complementary Angles: Two angles that add up to 90° (Ï€/2 radians).
    • Supplementary Angles: Two angles that add up to 180° (Ï€ radians).
    • Adjacent Angles: Two angles that share a common vertex and side.
  • Triangles:
    • Right Triangles: Triangles with one right angle (90°).
    • Oblique Triangles: Triangles that are not right triangles.

Sine, Cosine, and Tangent

  • Sine (sin): Ratio of the opposite side to the hypotenuse.
    • sin(A) = opposite side / hypotenuse
  • Cosine (cos): Ratio of the adjacent side to the hypotenuse.
    • cos(A) = adjacent side / hypotenuse
  • Tangent (tan): Ratio of the opposite side to the adjacent side.
    • tan(A) = opposite side / adjacent side
  • SOH-CAH-TOA: A mnemonic to remember the trig ratios:
    • Sine = Opposite / Hypotenuse
    • Cosine = Adjacent / Hypotenuse
    • Tangent = Opposite / Adjacent

Trigonometric Identities

  • Pythagorean Identity:
    • sin²(A) + cos²(A) = 1
  • Sum and Difference Identities:
    • sin(A + B) = sin(A)cos(B) + cos(A)sin(B)
    • sin(A - B) = sin(A)cos(B) - cos(A)sin(B)
    • cos(A + B) = cos(A)cos(B) - sin(A)sin(B)
    • cos(A - B) = cos(A)cos(B) + sin(A)sin(B)
  • Double Angle Identities:
    • sin(2A) = 2sin(A)cos(A)
    • cos(2A) = cos²(A) - sin²(A)

Angles and Triangles

  • Angles can be measured in degrees or radians, with 1 radian equivalent to 180/Ï€ degrees.
  • Complementary angles are two angles that add up to 90° (Ï€/2 radians).
  • Supplementary angles are two angles that add up to 180° (Ï€ radians).
  • Adjacent angles are two angles that share a common vertex and side.
  • Right triangles have one right angle (90°).
  • Oblique triangles are triangles that are not right triangles.

Sine, Cosine, and Tangent

  • Sine (sin) is the ratio of the opposite side to the hypotenuse, calculated as sin(A) = opposite side / hypotenuse.
  • Cosine (cos) is the ratio of the adjacent side to the hypotenuse, calculated as cos(A) = adjacent side / hypotenuse.
  • Tangent (tan) is the ratio of the opposite side to the adjacent side, calculated as tan(A) = opposite side / adjacent side.
  • The SOH-CAH-TOA mnemonic helps remember the trig ratios: Sine = Opposite / Hypotenuse, Cosine = Adjacent / Hypotenuse, Tangent = Opposite / Adjacent.

Trigonometric Identities

  • The Pythagorean Identity states that sin²(A) + cos²(A) = 1.
  • The Sum and Difference Identities are:
    • sin(A + B) = sin(A)cos(B) + cos(A)sin(B)
    • sin(A - B) = sin(A)cos(B) - cos(A)sin(B)
    • cos(A + B) = cos(A)cos(B) - sin(A)sin(B)
    • cos(A - B) = cos(A)cos(B) + sin(A)sin(B)
  • The Double Angle Identities are:
    • sin(2A) = 2sin(A)cos(A)
    • cos(2A) = cos²(A) - sin²(A)

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