Engineering Board Exam Reviewer · Solid Analytic Geometry · medium

Find the acute angle between the planes x+y+z=3 and x-y+z=5, in degrees.

  1. 19.47°
  2. 70.53°
  3. 54.74°
  4. 60°

Answer

B. 70.53°

Solution

The normals are (1,1,1) and (1,-1,1). =|1-1+1|/ 3 3= 13 =70.53°.

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