Question

- If 3 cot A = 4 then. find the
value of cos2 A - sin2 A.​

Answer 1

Step-by-step explanation:

I think this should be right:-

cot A=B/P(base and perpendicular resp.)

so if 3 cot A=4

than,cot A=4/3(B/P).

so by comparing B=4 and P=3.

by using Pythagoras theorem;

H^2=B^2+P^2

H=5.

Now we have H,

Now using cos2A=2cos^2A-1

and sin 2A=2sinAcosA

we can expand the given term.

By putting the respective values we get,cos2A=2(4/5)^2-1=(32/25)-1=7/25

and sin 2A=2(3/5)(4/5)=24/25

(7/25)-(24/25)=-17/25