This question was previously asked in

RRB JE Previous Paper 9 (Held On: 25 May 2019 Shift 1)

Option 2 : 0

RRB JE Previous Paper 1 (Held On: 22 May 2019 Shift 2)

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100 Questions
100 Marks
90 Mins

If sides ratio 1 : 1 : √2

If two sides are equal, so two angles will be equal.

One of three angles is 90, so the sum of the other two angles will be 90

A + B = 90

⇒ A = B

⇒ 2A = 90

⇒ A = 90/2

⇒ A = 45

As we know,

cos A cos B – sin A sin B

⇒ cos (A + B)

⇒ cos (45 + 45)

⇒ cos 90

⇒ 0