Q. In △KLM,k=550cm,m=540cm and ∠M=74∘. Find all possible values of ∠K, to the nearest 10th of a degree.Answer:
Given triangle KLM: We are given a triangle KLM with sides k=550cm, m=540cm, and angle M=74∘. We want to find the possible values of angle K. We can use the Law of Sines, which states that the ratio of the length of a side of a triangle to the sine of the angle opposite that side is the same for all three sides of the triangle.
Law of Sines: First, we write the Law of Sines for our triangle: (sin(K)/m)=(sin(M)/k)
Write Law of Sines: We plug in the known values: (sin(K)/540)=(sin(74∘)/550)
Plug in values: Now we solve for sin(K):sin(K)=(550sin(74∘))⋅540
Solve for sin(K): We calculate the value of sin(74∘) using a calculator:sin(74∘)≈0.9613
Calculate sin(74∘): We substitute this value into our equation:sin(K)=5500.9613×540
Substitute value: We perform the calculation: sin(K)≈(5500.9613)×540≈0.9419
Perform calculation: Now we find the angle K whose sine is approximately 0.9419. We use the inverse sine function (arcsin) on a calculator:K≈arcsin(0.9419)
Find angle K: We calculate the value of K:K≈70.5 degrees
Calculate value of extit{K}: However, since the sine function is positive in both the first and second quadrants, there is another possible value for angle extit{K}. It is the supplement of extit{70.5} degrees, which is extit{180} degrees - extit{70.5} degrees.
Find supplement of K: We calculate the supplement of K:K≈180 degrees −70.5 degrees ≈109.5 degrees
Calculate supplement of K: We now have two possible values for angle K: 70.5 degrees and 109.5 degrees. However, we must check if these values are valid by ensuring that the sum of angles in a triangle is 180 degrees.
Check validity of values: We add the known angle M and both possible values of angle K to see if they sum to 180 degrees: 74 degrees + 70.5 degrees + angle L = 180 degrees 74 degrees + 109.5 degrees + angle L = 180 degrees
Add angles: We solve for angle L in both cases:For K=70.5 degrees: angle L=180 degrees −74 degrees −70.5 degrees ≈35.5 degreesFor K=109.5 degrees: angle L=180 degrees −74 degrees −109.5 degrees K=70.50 degrees
Solve for angle L: The second case gives us a negative value for angle L, which is not possible in a triangle. Therefore, the only valid value for angle K is 70.5 degrees.
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