Question 932071
Draw right triangle and mark a point 17ft farther from the tree {{{b}}},the height of the tree {{{h}}}, angle off {{{36}}}° between horizontal line and sloping line mark with {{{theta}}}.

Then: 


the angle of elevation to the top of the tree was {{{48}}}°. Moving to a point {{{17ft}}} farther, the angle of elevation becomes {{{36}}}°.
{{{h=height}}}

{{{h=hight}}}

{{{b=base=xft}}}

{{{(theta)=48}}}°

{{{tan(theta)=h/x}}}

{{{x=h/tan(theta)}}}

{{{x=h/tan(48)}}}

{{{x=h/1.1106}}}

{{{h=1.1106x}}}...........eq.1

Moving to a point {{{17ft}}} farther, the angle of elevation becomes {{{36}}},° so we have: 

{{{b=base=xft+17ft}}}

{{{(theta)=36}}}°

{{{tan(theta)=h/(x+17ft)}}}

{{{h=(x+17ft)tan(theta)}}}

{{{h=x*tan(36)+17ft*tan(36)}}}    

{{{h=0.72654x+17ft*0.72654}}}

{{{h=0.72654x+12.35118ft}}}...........eq.2....

the left sides of eq.1=eq.2, so we have

{{{1.1106x=0.72654x+12.35118ft}}}...........solve for {{{h}}}

{{{1.1106x-0.72654x=12.35118ft}}}

{{{0.38406x=12.35118ft}}}

{{{x=12.35118ft/0.38406}}}

{{{x=32.16ft}}}

=> {{{b=base=xft+17ft}}}=> {{{b=32.16ft+17ft=49ft}}}

{{{h=49.16ft*tan(36)}}}

{{{h=49.16ft*0.38406}}}

{{{h=18.88ft}}} -the height of the tree