Quadrilateral ABCD has AB = BC = CD. Angle ABC = 70 degrees and Angle BCD = 170 degrees. What is the degree measure of angle BAD?

Could I just get some hints please?

Vicky.

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- November 12th 2009, 07:46 PMVicky1997Quadrilateral
Quadrilateral ABCD has AB = BC = CD. Angle ABC = 70 degrees and Angle BCD = 170 degrees. What is the degree measure of angle BAD?

Could I just get some hints please?

Vicky. - November 12th 2009, 10:07 PMWilmer
Let AB = BC = CD = 1

Use Sine Law and isosceles triangle BCD to calculate BD (you should get ~1.992)

Do you see that angle ABD = 65 (70 - 5) ?

Use Cosine Law and triangle ABD to calculate AD (you should get ~1.813)

We now have BD / sin(A) = AD / sin(65)

From that, calculate angle A (you should get 85 degrees.

If you draw a diagram, it'll be easier for you to follow above steps. - November 14th 2009, 10:22 AMVicky1997