Respuesta :
Answer:
fourth option
Step-by-step explanation:
Using the Law of Cosines in Δ STU to find s
s² = t² + u² - 2us cosS
where t = 9, u = 10 and S = 100° , thus
s² = 9² + 10² - 2(9)(10)cos100°
The required law of cosines is [tex]s^{2}=9^{2} +10^{2}-2(9)(10)Cos(100)[/tex]
What is the law of cosines ?
The relation between lengths of sides of the triangle and cosines of the angles of the triangle is called law of cosines.
This law is used for SAS triangles.
The formula of law of cosines is [tex]a^{2}= b^{2}+ c^{2}-2(b)(c)Cos(A)[/tex]
Where a, b, c are sides of the triangle and A is the opposite angle of side a.
What is the length of s ?
Here in the given diagram,
SU = 9 unit, ST = 10 unit & UT = s
Also given that, ∠S = 100°
Using the law of cosines,
[tex]UT^{2} =SU^{2}+ ST^{2}-2(SU)(ST)Cos(S)[/tex]
⇒ [tex]s^{2}=9^{2} +10^{2}-2(9)(10)Cos(100)[/tex]
4th option is correct.
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