Law of Cosines

Question 1

The law of cosines is used to find the measure of .

Revolt · Accepted Answer

44º

Question 2

Law of cosines: a2 = b2 + c2 – 2bccos(A)

Revolt · Accepted Answer

64°

Question 3

A parallelogram has side lengths of 13 and 17 and an angle that measures 64°.Law of cosines: a2 = b2 + c2 – 2bccos(A)

Revolt · Accepted Answer

16

Question 4

Law of cosines: a2 = b2 + c2 – 2bccos(A)

Revolt · Accepted Answer

33°

Question 5

Abby used the law of cosines for KMN to solve for k.k2 = 312 + 532 – 2(31)(53)cos(37°)Law of cosines: a2 = b2 + c2 – 2bccos(A)

Revolt · Accepted Answer

mK = 37° and n = 31

Question 6

Consider the proof.Given: In △ABC, BD ⊥ ACProve: the formula for the law of cosines, a2 = b2 + c2 – 2bccos(A) Statement Reason1.In △ABC, BD ⊥ AC1.given2.In △ADB, c2 = x2 + h22.Pythagorean thm. 3.In △BDC, a2 = (b – x)2 + h23.Pythagorean thm. 4.a2 = b2 – 2bx + x2 + h24.prop. of multiplication5.a2 = b2 – 2bx + c25.substitution6.In △ADB, cos(A) = 6.def. cosine7.ccos(A) = x7.mult. prop. of equality8.a2 = b2 – 2bccos(A) + c28.?9.a2 = b2 + c2 – 2bccos(A)9.commutative propertyWhat is the missing reason in Step 8?

Revolt · Accepted Answer

substitution

Law of Cosines Answers

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