Question of The Day24-08-2020

What will be the value of (1 – cot 230) (cot 220 – 1)?

Correct Answer : b ) $$– 2$$

Explanation :

Consider A + B = 450

Taking cot on both the sides

cot (A + B) = cot 450

$$\frac {cotAcotB-1 }{cotA+cotB}=1$$

cot A cot B – 1 = cot A + cot B

cot A cot B – cot A – cot B = 1

Adding 1 on both the side

cot A cot B – cot A – cot B + 1 = 1 + 1

(cot A – 1) (cot B – 1) = 2

So, when A + B = 450, then (cot A – 1) (cot B – 1) = 2

According to the question,

Let A = 230 and B = 220

A + B = 450

So, (cot 230 – 1) (cot 220 – 1) = 2

And, (1 – cot 230) (cot 220 – 1) = – 2

Hence, (b) is the correct answer.

Such type of question is asked in various government exams like SSC CGL, SSC MTS, SSC CPO, SSC CHSL, RRB JE, RRB NTPC, RRB GROUP D, RRB OFFICER SCALE-I, IBPS PO, IBPS SO, RRB Office Assistant, IBPS Clerk, RBI Assistant, IBPS RRB OFFICER SCALE 2&3, UPSC CDS, UPSC NDA, UP SI etc.

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