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8. Sequences and Series
normal
If all interior angle of quadrilateral are in $AP$ . If common difference is $10^o$ , then find smallest angle ?.....$^o$
A
$60$
B
$70$
C
$120$
D
$75$
Solution
Common differcuce in angle $(\phi)=10^{\circ}$ let $4$ angles in $A.P.$ area atd, $a+2d, a+3 d=$ and sum are,
$a+a+d+a+2 d+a+3 d=360^{\circ}$
$4 a+c d=360^{\circ}$
$4 a=360^{\circ}-6 d=360^{\circ}-60^{\circ}$
$4 a=380^{\circ}$
$a=75^{\circ}$
Standard 11
Mathematics