Question

In∆ABC,<ACD=105° be an exterior angle of it.If <A=<B=3:4,find <A​

Answer 1

Answer:

ok see this carefully

and understand,

hope it helps you

thank you ☺✌

Answer 2

Explanation-

<ACD is an exterior angle. it means <ACB+<ACD=180°

=> <ACB+105°=180°

=> <ACB=180°-105°=75°

<A=<B=3:4

let <A=3x and <B=4x

we know that in triangle

<A+<B+<C=180°

=> 3x+4x+75°=180°

=> 7x+75°=180°

=> 7x=180°-75°

=> 7x=105°

=> x=105°/7=15°

=> 3x= 15°×3=45°

as a short cut-

<A+<B=<ACD(because the exterior angle is the sum of other two angle which is on the opposite of it)

=> 3x+4x=105°

=>7x=105°

Then solve as upper.

Thank you.