Question

In triangle ABC, angle ABC =135* , AB=18 , BC =12 then find area of triangle ABC .​

Answer 1

Give : ΔABC   AB = 18  , BC = 12 ,  ∠ B = 135°

To Find :  Area of Triangle ΔABC

Solution:

Area of Triangle with two sides and included angle

= (1/2) AB * BC * Sin ∠B

AB = 18

BC  = 12

∠B  = 135°

Area of ΔABC  = (1/2) 18 (12) Sin135°

= 9 (12) Sin45°    (∵ Sin x° = Sin(180° - x°) )

= 108 Sin45°

Sin45°  = 1/√2

=108 / √2

= 54√2

Area of ΔABC  =   54√2 sq units

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