Topic Details (Notes format)

How to Use the Pythagorean Identities in Trigonometry

Subject: Mathematics

Book: Maths Mastery

Key Pythagorean trig identities include sin²(θ) + cos²(θ) = 1, 1 + tan²(θ) = sec²(θ), and 1 + cot²(θ) = csc²(θ). These relationships allow you to convert between trigonometric functions or simplify complicated expressions. For example, if sin(θ) = 3/5, then cos(θ) = √(1 – sin²(θ)) = √(1 – 9/25) = √(16/25) = 4/5. This knowledge extends to verifying trigonometric proofs, analyzing wave functions in physics, or building engineering models that rely on sinusoidal behaviors. Familiarity with Pythagorean identities significantly eases advanced problem-solving in calculus and beyond.

Practice Questions

A rectangle has a length of 10 cm and a width of 5 cm. What is the diagonal of the rectangle?

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If sin(θ) = 3/5 and θ is an acute angle, what is tan(θ)?

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If x^2 - 6x + 9 = 0, what is the value of x?

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A cube has a side length of 4 cm. What is its volume?

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If 2a + b = 10 and a - b = 4, what is the value of a?

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If 3x = 81, what is the value of x?

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A sphere has a radius of 7 cm. What is its volume?

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If the perimeter of a square is 36 cm, what is the length of its diagonal?

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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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If a cylinder has a radius of 7 cm and height of 10 cm, what is its volume?

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