Isosceles 81130

The angle at the apex of an isosceles triangle is 78°. Base 28.5cm. Shoulder length?

Correct answer:

r =  17.5973 cm

Step-by-step explanation:

a=28.5 cm γ=78  ω=γ/2=78/2=39   tan ω = a/2 : r  r=a/2 cotgω=a/2 cotg39° =28.5/2 cotg39° =28.5/2 cotg(ω)=17.597=17.5973 cm

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