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  1. ABC is a right angled triangle with ∠A = 90°. Then the value of cos²A + cos²B + cos²C is :
    1. 2
    2. 1
    3. 0
    4. 3
Correct Option: B


∠CAB = 90°
∴ cosA = cos 90° = 0

cosB =
AB
, cosC =
AC
BCBC

∴ cos²A + cos²B + cos²C
= 0 +
AB²
 +
AC²
BC²BC²

=
AB² + AC²
 =
BC²
 = 1
BC²BC²


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