Answer for Day 27 Math Problem

19 / 32 or 0.59375 🎯

Any of the two answers above shall be accepted.

Solution

The problem is under (plane) trigonometry.

We will use the double angle identity sin (2A) = 2 * sin (A) * cos (A), where we will solve for cos (A), which is cos (A) = sin (2A) / sin (A) / 2.

cos (A) = sin (2A) / sin (A) / 2
cos (A) = (19 / 20) / (4 / 5) / 2
cos (A) = 19 / 32

The exact value of cos (A) is 19 / 32 or 0.59375.

(The angle A is approximately 53.58° using the arccos function.)

Can we arrive at the same answer while not directly using the double angle identity? 🤔

Winner: @jfang003 🏅

1 HIVE has been sent to @jfang003's Hive account. 💰

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