obtuse triangle ABC with obtuse angle B. Point D on side AC such that angle BDC is also obtuse. Angle DAB is 2/3 of angle ABD. Angle BCD is 1/5 of angle CBD is 4 more than angle BAD. Find the measure of angle ABC.
The wording of " Angle BCD is 1/5 of angle CBD is 4 more than angle BAD." is rather ambiguous.
Did you mean
" Angle BCD is 1/5 of angle CBD, AND IT is 4 more than angle BAD." ?
yes
Ok, let me use < for angle
Let <ABD = 3x (I can avoid fractions this way)
then <DAB = 2x
by exterior angle theorem <BDC = 5x
<BCD = 2x + 4 (it said so)
<CBD is 5 times <BCD (it said so)
so <CBD = 5(2x+4) = 10x + 20
so by exterior angle theorem :
< BDC = 12x + 24
But CDA is a straight line, so
5x + 12x+24 = 180
x = 216/7 or 9.1765
then <ABC = 10x+20 + 3x
= 13x + 20 = 139.294°
let's check the rest
<ABD = 27.529
<BAD = 18.353
and 18.535/27.529 = .6666678 or 2/3
< BDA = 134.118
for a total sum of 134.118+27.529+18.353 = 180
In triangle BDC
<C = 4 more than <BAD = 22.353
which is 1/5 of <CBD making
<CBD = 111.765
Also we knew that <BDC = 5x = 45.882
check: is CDA a straight line?
is 17x+24 = 180 ?
17x + 24 = 17(9.1765) + 24 = 180.0005 , OK
what about the sum of angles in that triangle?
what is 111.765+45.882+22.353 = 180
So again
<ABC = 10x+20 + 3x
= 13x + 20 = 139.294°
To find the measure of angle ABC, let's use the given information to solve step by step:
1. Let's denote angle ABC as x.
2. According to the given information, angle BCD is 1/5 of angle CBD, and angle CBD is 4 more than angle BAD. So, angle BCD = (1/5) * (angle CBD + 4).
3. We also know that angle DAB is 2/3 of angle ABD. Let's denote angle ABD as y. So, angle DAB = (2/3) * y.
4. Since we have an obtuse triangle, we know that the sum of the three angles in a triangle is 180 degrees.
Using this information, we can set up the equation:
x + y + (1/5) * (angle CBD + 4) + (2/3) * y = 180
Now, let's simplify the equation:
x + y + (1/5) * angle CBD + (4/5) + (2/3) * y = 180
To continue, we need more information.