trig 2

william · #1 $Old$ January 11th, 2009, 08:14 PM

1.A ship sees a lighthouse which is found to be 9.8 km distant through the use of radar. The lighthouse is 3km from a second lighthouse. The angle between the line of sight between the two lighthouses is 30°. What is the angle between the line of sight between the ship and lighthouse 2, when looking from lighthouse 1?

2.In a triangle ABC, side a is 18cm long, side b is 10cm long and angle B is 89°. What is the measure of angle A?

earboth · #2 $Old$ January 12th, 2009, 02:37 AM

Quote:

Originally Posted by william $View Post$

1.A ship sees a lighthouse which is found to be 9.8 km distant through the use of radar. The lighthouse is 3km from a second lighthouse. The angle between the line of sight between the two lighthouses is 30°. What is the angle between the line of sight between the ship and lighthouse 2, when looking from lighthouse 1?

2.In a triangle ABC, side a is 18cm long, side b is 10cm long and angle B is 89°. What is the measure of angle A?

With the values given in both questions you can't construct a triangle and therefore you can't calculate any additional values. (Conflict with congruence rule SSA)

I've attached the construction for #1.

TheMasterMind · #3 $Old$ January 12th, 2009, 02:17 PM

Quote:

Originally Posted by earboth $View Post$

With the values given in both questions you can't construct a triangle and therefore you can't calculate any additional values. (Conflict with congruence rule SSA)

I've attached the construction for #1.

earboth please consider my diagram, does it appeal to you?

earboth · #4 $Old$ January 13th, 2009, 12:59 AM

Quote:

Originally Posted by TheMasterMind $View Post$

earboth please consider my diagram, does it appeal to you?

To #1:
You know 2 sides and one angle of the triangle in question. The angle is opposite the smaller side. Thus you can't draw congruent triangles with the given properties, because for the congruence rule SSA the given angle has to be opposite the greater side (of the two given sides).

To your drawing: Your angle of 30° is correct for very small values of 30

. I've attached an acurate drawing with all measures.

TheMasterMind · #5 $Old$ January 13th, 2009, 07:20 PM

Quote:

Originally Posted by earboth $View Post$

To #1:
You know 2 sides and one angle of the triangle in question. The angle is opposite the smaller side. Thus you can't draw congruent triangles with the given properties, because for the congruence rule SSA the given angle has to be opposite the greater side (of the two given sides).

To your drawing: Your angle of 30° is correct for very small values of 30

. I've attached an acurate drawing with all measures.

I've never encountered/learned this rule, please excuse my misunderstanding