Topic Details (Notes format)

How to Use Sum and Difference Identities (Sine, Cosine, Tangent)

Subject: Mathematics

Book: Maths Mastery

Trigonometric sum/difference formulas let you calculate sin(A±B), cos(A±B), tan(A±B) from sin, cos, tan of A and B. For instance, sin(A + B)=sin(A)cos(B)+cos(A)sin(B). A practical scenario: if sin(A) and cos(B) are known, you can find sin(A + B) quickly. These identities fuel transformations, equation solving, and geometry proofs. They also apply to signal processing (phase shifts) and physics (wave interference). Mastering them expands your capacity to handle angles beyond standard reference angles, bridging simpler known values to more complex angle relationships.

Practice Questions

If a + b = 10 and ab = 21, what is the value of a^2 + b^2?

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If sin(A) = 3/5 and cos(B) = 5/13, where A and B are acute angles, what is sin(A+B)?

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The probability of rolling a sum of 7 with two dice is:

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If a:b = 5:7 and b:c = 6:11, what is a:c?

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If x^2 + 4x + 4 = 0, what is the value of x?

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If the radius of a circle is doubled, what happens to its area?

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The sides of a triangle are 13 cm, 14 cm, and 15 cm. What is its area?

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The probability of getting an even number when rolling a die is:

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If the ratio of two numbers is 3:5 and their HCF is 4, what are the numbers?

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If a person can type 45 words per minute, how many words can they type in 2 hours?

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