Q. In ΔGHI,g=9.8cm,i=9.6cm and ∠I=43∘. Find all possible values of ∠G, to the nearest 10th of a degree.Answer:
Law of Sines Formula: To find the possible values of angle G, 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 opposite angle is constant for all three sides and angles in the triangle. The formula is:sin(A)a=sin(B)b=sin(C)cwhere a, b, and c are the lengths of the sides, and A, B, and C are the opposite angles. In our case, we have:sin(G)g=sin(I)iWe can plug in the values we know to find sin(G):sin(G)9.8=sin(43 degrees)9.6First, we calculate sin(43 degrees):sin(43 degrees)≈0.682Now we can solve for sin(G):sin(G)=9.69.8×sin(43 degrees)sin(G)≈9.69.8×0.682sin(G)≈9.66.6884sin(G)≈0.6967
Calculating sin(G): Now that we have the value of sin(G), we can find angle G by taking the inverse sine (arcsin) of sin(G). However, since the sine function is positive in both the first and second quadrants, there are two possible angles for G that have the same sine value. These angles are supplementary, meaning they add up to 180 degrees. We will find the first angle, which is the acute angle:G≈arcsin(0.6967)G≈44.4 degrees (to the nearest tenth)
Finding Angle G: To find the second possible value for angle G, we subtract the first value from 180 degrees:180 degrees −44.4 degrees =135.6 degreesSo the second possible value for angle G is 135.6 degrees (to the nearest tenth).
Checking Validity: We must now check if the second possible value for angle G is valid by ensuring that the sum of angles in a triangle is 180 degrees. We already have angle I as 43 degrees, and we need to check if angle H can be a positive acute angle when angle G is 135.6 degrees.Sum of angles in a triangle = 180 degreesAngle H = 180 degrees - Angle G - Angle IAngle H = 180 degrees - 135.6 degrees - 43 degreesAngle H = 1807 degreesSince angle H is positive and less than 180 degrees, the second value for angle G is valid.
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