Expert: Chen Min - 5/2/2008

Question
QUESTION: pls do help me
i had finish answering the number 11 question but i cant answer #12 letter c is definitely wrong

ANSWER: This is actually about functions.

The gradient of any linear function is the tangent of the angle between the graph(linear) and X-axis.

Let the angle between the line in first function and x-axis be A, and that of the second be B

The angle you need to get is the absolute value of B-A  (the second line is steeper,you'll observe. ) In this case,

tan A = 4/3,  tan B = 4; (obtained from the expressions of the functions)

tan (B - A) = (tan B - tan A) / (1 ＋ tan A tan B)

After you get the value of tan(B - A), just get the value of B - A with a calculator.

A is the answer ( Remember 22.83 degree = 22*50' )

Hope this helps:)

BTW, since you can slash out C, why not straight away put A? The question obviously commits a big mistake by providing two obtuse angles while it asks for an acute one...

---------- FOLLOW-UP ----------

QUESTION: thank you for your last answer ,really appreciate it ,im kinda confused bout answering questions with multiple choices ,can you check it,my answer would be letter b,i know that letter d is wrong thanks again

Answer
You're welcome.Helping you is my pleasure:)

This is quite an interesting question...All the choices satisfy the coordinates of point D.

Again, get the angle of inclination using the gradient.

Since the angle of inclination is 60 degrees, the tangent value, or the gradient of the line in equivalence, is tan 60 = 1.73205..Somehow, I think C is correct...

Gradient of A: 0.8660
         B: 1.15469
         C: 1.73205
         D: 0.57735

Usually all these long and fancy number only serve to distract you. Focus on one direction and you'll get the answer.

One thing: here 1.73205 is square root 3, and 0.86603 is its halved value. Sometimes see through the tricks in the question helps strengthening your confidence in answering:)

Hope this helps.