Posted by **Nicole** on Tuesday, December 18, 2012 at 10:11pm.

If the given point is on the terminal arm of an angle A in standard position, angle A is greater than or equal to 0 degrees and it is less than or equal to 180 degrees, find the measure of angle A, to the nearest tenth of a degree.

a) (4,3)

b) (12,5)

c) (-6,8)

d) (-24,7)

PLEASE help me!! with the steps and all i have no idea about this... thankyou so much!!

- math:) -
**Reiny**, Tuesday, December 18, 2012 at 10:29pm
If you are just learning this, I suggest you make a sketch of the right-angled triangle

a) and b) will be in quadrant I

c) and d) will be in quadrant II

I will do b) and c)

b) by Pythagoras, it is easy to find the hypotenuse to be 13

since cosØ = 12/13

use the cosine inverse of your calculator...

enter:

2nd

cos

(12÷13)

= to get appr 22.62° or 23°

c) hypotenuse^2 = (-6)^2 + 8^2 = 100

hypot = √100 = 10

cosØ = -6/10 = -3/5 or -.6

enter:

2nd

cos

(-.6)

=

to get 126.87° or 127°

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