Question

in triangle abc if AB + BC equals to 7 cm equals to 5 cm and Angle b equals to 90 degree, find cos a

Answer 1

Given :  AB + BC = 7 cm ∠ B = 90°  AC = 5 cm

To find Cos A

Solution:

Let say AB = x

then BC = 7 - x

AC² = AB² + BC²

=> 5² = x² +  (7 - x)²

=> 25 = x²  + 49 + x²  - 14x

=>  2x² - 14x  + 24 = 0

=> x² - 7x + 12 = 0

=> x² - 3x - 4x + 12 = 0

=> x(x - 3) - 4(x - 3) = 0

=> (x - 4)(x - 3) = 0

=> x = 4  , x = 3

Case 1 x = 4  => AB = 4 cm  & BC = 3cm

Case 2 x = 3 => AB = 3 cm  & BC = 4 cm

Cos A = AB /  AC

=> CosA  = 4/5  or  3/5

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Answer 2

Answer:-

step by step explanation:-

hope it's helpful to you!!