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Ch. 2 - Acute Angles and Right Triangles
Lial - Trigonometry 12th Edition
Lial12th EditionTrigonometryISBN: 9780136552161당신이 사용하는 게 아니라요?교과서 변경
3장, 문제 2.R.40

Determine whether each statement is true or false. If false, tell why. Use a calculator for Exercises 39 and 42. 1 tan² 60° = sec² 60°

검증된 단계별 안내
1
Recall the Pythagorean identity involving tangent and secant: \(\tan^2 \theta + 1 = \sec^2 \theta\).
Substitute \(\theta = 60^\circ\) into the identity to get \(\tan^2 60^\circ + 1 = \sec^2 60^\circ\).
Compare the given statement \(\tan^2 60^\circ = \sec^2 60^\circ\) with the identity. Notice that the identity includes an additional \(+1\) on the left side.
Calculate or recall the exact values: \(\tan 60^\circ = \sqrt{3}\), so \(\tan^2 60^\circ = 3\), and \(\sec 60^\circ = 2\), so \(\sec^2 60^\circ = 4\).
Since \(\tan^2 60^\circ = 3\) and \(\sec^2 60^\circ = 4\), the statement \(\tan^2 60^\circ = \sec^2 60^\circ\) is false because it ignores the \(+1\) in the Pythagorean identity.

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이 영상 해법은 위 문제에 도움이 된다고 튜터들이 추천한 것입니다.
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주요 개념

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Pythagorean Identity involving Tangent and Secant

The identity tan²θ + 1 = sec²θ relates the tangent and secant functions. It means that the square of the tangent of an angle plus one equals the square of the secant of the same angle. This identity is fundamental for verifying trigonometric equations involving these functions.
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Pythagorean Identities

Evaluating Trigonometric Functions at Specific Angles

To verify statements like tan² 60° = sec² 60°, you must calculate the exact or approximate values of tangent and secant at 60 degrees. Knowing that tan 60° = √3 and sec 60° = 2 helps in substituting and comparing both sides of the equation.
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Evaluate Composite Functions - Special Cases

Use of Calculators for Trigonometric Verification

Calculators can provide decimal approximations of trigonometric values, which is useful for checking the truth of equations when exact values are complex or unknown. Using a calculator ensures accuracy in evaluating tan² 60° and sec² 60° for comparison.
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How to Use a Calculator for Trig Functions