Solved Prove the following identities: cos pi/8 = 1/2 | Chegg.com
Solved Use a half-angle formula to find the exact value of | Chegg.com
Proof that 22/7 exceeds π - Wikipedia
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Trigonometry Angles--Pi/8 -- from Wolfram MathWorld
Find the value of tan pi/8 - Maths - Trigonometric Functions - 13447383 | Meritnation.com