Question

find the angle between the lines 3x+y+15=0 and x+y+11=0​

Answer 1

Answer:

3x+y−7=0 and x+2y+9=0

write in the form y=mx+c

i.e.y=−3x+7,y=

2

−x

−

2

9

∴m

1

=−3 and m

2

∓−

2

1

tan(A−B)=

∣

∣

∣

∣

∣

1+tanAtanB

tanA−tanB

∣

∣

∣

∣

∣

∣

∣

∣

∣

∣

1+(−3)(−y

2

)

−3−(−y

2

)

∣

∣

∣

∣

∣

=

∣

∣

∣

∣

∣

5/2

−5/2

∣

∣

∣

∣

∣

=1

∴ Angle b/w then is tan

−1

(1)=45

∘

=

4

π