Maths-
General
Easy

Question

The angles of a triangle are in the ratio 3:5:10. Then ratio of smallest to greatest side is

  1. 1 colon s i n invisible function application 10 to the power of ring operator
  2. 1 colon 2 s i n invisible function application 10 to the power of 6
  3. 1 colon c o s invisible function application 10 to the power of ring operator
  4. 1 colon 2 c o s invisible function application 10 to the power of ring operator

hintHint:

In this question first we have to find the angles of the triangle. Then use the sine rule to find the ratio of largest to smallest side.

The correct answer is: 1 colon 2 c o s invisible function application 10 to the power of ring operator


    Step1: Finding the angles of the triangles.
    Let the angles be 3 x comma 5 x and 10 x.
    Let ABC be the triangle with angle A equals 3 x comma space angle B equals 5 x and angle C equals 10 x and the side opposite to angle A comma angle B comma angle C are a comma b comma c respectively.
    By using the theorem : Side opposite to greatest angle will be largest
    The sum of all the angles of a triangles is 180 degree
    =>3 x plus 5 x plus 10 x space equals space 180 degree
    =>x equals 10 degree
    angle A equals space 3 cross times 10 equals 30 degree
angle B equals 5 cross times 10 equals 50 degree
angle C equals 10 cross times 10 equals 100 degree
    Step2: Find the ratio of the largest to smallest side.
    By using sine rule,
    fraction numerator sin open parentheses A close parentheses over denominator a end fraction equals fraction numerator sin open parentheses B close parentheses over denominator b end fraction equals fraction numerator sin open parentheses C close parentheses over denominator c end fraction
    We have to find the ratio of c over a.
    fraction numerator sin open parentheses 30 degree close parentheses over denominator a end fraction equals fraction numerator sin open parentheses 50 degree close parentheses over denominator b end fraction equals fraction numerator sin open parentheses 100 degree close parentheses over denominator c end fraction
    We know that sin open parentheses 90 degree plus theta close parentheses equals cos open parentheses theta degree close parentheses
    sin open parentheses 100 degree close parentheses equals sin open parentheses 90 degree plus 10 degree close parentheses
    =>cos open parentheses 10 degree close parentheses
    =>fraction numerator 1 over denominator 2 a end fraction equals fraction numerator sin open parentheses 50 degree close parentheses over denominator b end fraction equals fraction numerator cos open parentheses 10 degree close parentheses over denominator c end fraction
    =>c over a equals 2 cos open parentheses 10 degree close parentheses

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