In A B C, a=2 cm, b=3 cm and c=4 cm, then angle A is - Vidyadip

MCQ

In $\triangle A B C, a=2 cm, b=3 cm$ and $c=4 cm$, then angle A is

A
$\cos ^{-1}\left(\frac{1}{24}\right)$
B
$\cos ^{-1}\left(\frac{11}{16}\right)$
✓
$\cos ^{-1}\left(\frac{7}{8}\right)$
D
$\cos ^{-1}\left(-\frac{1}{4}\right)$

✓

Answer

Correct option: C.

$\cos ^{-1}\left(\frac{7}{8}\right)$

(C) $\cos A=\frac{b^2+c^2-a^2}{2 b c}=\frac{9+16-4}{2 \times 3 \times 4}=\frac{7}{8}$
$\Rightarrow A =\cos ^{-1}\left(\frac{7}{8}\right)$

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