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If in an isosceles triangle with base 'a...

If in an isosceles triangle with base 'a', vertical angle `20^@` and lateral side each of length 'b' is given then value of `a^3+b^3` equals

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We have `sin 10^(@)=(a)/(2b)`
Now `sin 30^(@)=3sin 10^(@)-4sin^(3)10^(@)`
`rArr(1)/(2)=(3a)/(2b)-(4a^(3))/(8b^(3))`
`rArr 1=(3a)/(b)-(a^(3))/(b^(3))`
`rArr a^(3)+b^(3)=3ab^(2)`
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