SSC CHSL 15 Nov 2015 Shift 2 Paper

Question : 104 of 200

Marks: +1, -0

If A, B and C be the angles of a triangle, then out of the following, the incorrect relation is:

Solution:

If A, B and C be the angles of a triangle, then

∠A+∠b+ ∠c=180°

⇒

∠A+∠b=180°-∠C

⇒

{∠A+∠B}/2=90°-∠C/2

----(i)
(A) :

tan( {A+B}/2 ) =tan(90 ° − ∠C/2 )

= cot( ∠C /2 ) ≠ sec( ∠C/2 )

(B) :

cot({A+B} /2 )

=cot(90 ∘ − ∠C/2 ) = tan(∠C/2)

sin( {A+B}/2 ) =sin(90° − ∠C/2 )

= cos( ∠C/2 )

(D) :

cos( {A+B}/2 )=cos(90° −∠C/ 2 )

= sin∠C /2

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