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Type: Multiple-Choice
Category: Trigonometry
Level: Grade 11
Standards: HSG-SRT.D.10
Author: nsharp1
Created: 4 years ago

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Trigonometry Question

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The questions below concern the following proof.


Let ΔABC be an obtuse triangle, such that mBAC>90°. Let mA refer to mBAC and mB refer to mABC. Prove the law of sines, ABsin(mC)=BCsin(mA)=ACsin(mB).

Obtuse Triangle ABC v2

Statement Reason
1.Construct altitude ¯AD such that point D lies on ¯BC1.
2.¯AD¯BC2.Definition of an altitude
3.ADC, ADB are right angles3.Definition of perpendicular lines
4.ΔADC, ΔADB are right triangles4.Definition of right triangles
5.5.Sine ratio in a right triangle
6.ABsin(mB)=AD6.Multiplication Property of Equality
7.7.Sine ratio in a right triangle
8.ACsin(mC)=AD8.Multiplication Property of Equality
9.ABsin(mB)=ACsin(mC)9.Transitive Property of Equality
10.AB=ACsin(mC)sin(mB)10.Division Property of Equality
11.ABsin(mC)=ACsin(mB)11.Division Property of Equality
12.Extend ¯AC to AC12.
13.Construct altitude ¯BE such that point E lies on AC    (E lies on AC such that AE+AC=CE)13.
14.¯BE¯CE14.Definition of an altitude
15.BEC is a right angle15.Definition of perpendicular lines
16.ΔAEB, ΔBEC are right triangles16.Definition of right triangles
17.17.Sine ratio in a right triangle
18.ABsin(mBAE)=BE18.Multiplication Property of Equality   
19.19.Sine ratio in a right triangle
20.BCsin(mC)=BE20.Multiplication Property of Equality
21.BCsin(mC)=ABsin(mBAE)21.Transitive Property of Equality
22.mBAE+mA=180°22.
23.mBAE=180°-mA23.Subtraction Property of Equality
24.BCsin(mC)=ABsin(180°-mA)24.Substitution Property of Equality
25.BCsin(mC)=ABsin(mA)25.Trig Identity
26.BCsin(mC)sin(mA)=AB26.Division Property of Equality
27.BCsin(mA)=ABsin(mC)27.Division Property of Equality
28.BCsin(mA)=ACsin(mB)28.Transitive Property of Equality
29.ABsin(mC)=BCsin(mA)=ACsin(mB)29.Combined results

Grade 11 Trigonometry CCSS: HSG-SRT.D.10

What is the missing statement in step 17?
  1. sin(mBAE)=AEAB
  2. sin(mBAE)=BEAB
  3. sin(mBAE)=BEBC
  4. sin(mBAE)=BEAE