Page 30 - 11-Math-12 Application of Trigonometry

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3. Find the area of the triangle ABC, given three sides:

i) a = 18 , b =24 , c = 30

ii) a = 524 , b =276 , c = 315

iii) a = 32.65 , b =42.81 , c = 64.92

4. The area of triangle is 2437. If a = 79, and c = 97, then find angle b .

5. The area of triangle is 121.34. If a = 32° 15 b = 65° 37 then find c and angle g.

6. One side of a triangular garden is 30 m. If its two corner angles are 22 12 and 112 12 , find
the cost of planting the grass at the rate of Rs. 5 per square meter.

12.9 Circles Connected with Triangle

In our previous classes, we have learnt the methods of drawing the following three kinds

of circles related to a triangle:

i) Circum-Circle ii) In-Circle iii) Ex-Circle.

12.9.1 Circum-Circle:

The circle passing through the three vertices of a triangle is called a Circum- Circle. Its
centre is called the circum-centre, which is the point of intersection of the right bisectors of
the sides of the triangle. Its radius is called the circum-radius and is denoted by R.

a) Prove th=at: R =a =b c with usual notations.
2 sin a 2 sin b 2 sin g

version: 1.1

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