Geometry · Similarity, Right Triangles & Trigonometry

Calculate/use tangent

Calculate/use tangent.

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What you’ll learn

Calculate/use tangent.

Key idea

The defining ratio for tan is opposite/adjacent.

Tangent uses both legs and may exceed one; inverting a ratio changes its meaning.

Worked example

Enter the exact value or ordered values in the format requested below.

A right triangle has opposite=36, adjacent=15, hypotenuse=39 relative to acute theta. Compute tan(theta) exactly.

  1. tan(theta)=opposite/adjacent=36/15.
  2. The exact ratio is 12/5; the named side roles determine the order.

Answer: 12/5

Quick Check

Evaluate a worked attempt at calculate/use tangent, identify the first invalid step, and provide the correction.

A right triangle has opposite=21, adjacent=20, hypotenuse=29 relative to acute theta. Student Step 1 defines tan(theta)=adjacent/opposite. Step 2 substitutes to get 20/21. Locate the first invalid step and correct the ratio.

Choose one answer

Show a hint

Label sides relative to the specified acute angle, not their position on the page.