4.2.4 Approximations Using Phi

In addition to the π and e approximations found in Section 2.1.8, φ (phi) is a constant that has occasionally been asked in recent exams.

Key Approximations

Expression	Approximate Value
φ	1.618…
φ²	≈ 2.6
φ³	≈ 4.2
φ⁵	≈ 11
φ^φ	≈ 2.2
π × φ	≈ 5
e × φ	≈ 4.4
π × e × φ	≈ 13.8

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Problem Set 4.2.4

Practice these problems. Type your answer and press Enter to check: