Numbers are the same

Geometry Level 2

cos 1 > cos 1 cos 2 > cos 2 sin 1 > sin 1 sin 2 > sin 2 \cos1 > \cos1^\circ \\ \cos2 > \cos2^\circ \\ \sin1 > \sin1^\circ \\ \sin2 > \sin2^\circ

State the above statements as True or False from the top down to the bottom. T is for True and F is for False statement.

TTFF FFFF FFTT None of the given choices. FTFT TFTF TTTT

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2 solutions

Abhishek Sharma
Jun 3, 2015

As cosx is decreasing function between 0 and pi therefore statement 1 and statement 2 are false.

Also sinx is increasing function between 0 and pi/2 therefore statement 3 is true.

Now for statement 4, 2 radian is closer to pi/2 than pi therefore it has value close to 1 and sin 1 degree has value nearly 0 therefore statement 4 is true.

Moderator note:

Correct! Although it would be better to clarify this line

Now for statement 4, 2 radian is closer to pi/2 than pi

Actually which one is radiant? In my country we are using pi for radiant.

Hafizh Ahsan Permana - 6 years ago

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If there is a circle sign: \circ as a superscript of the number, then it is in degrees, else it's a convention to treat it as radians.

Pi Han Goh - 6 years ago

In general, for x [ 0 , π ] { cos x 1 < cos x 2 if x 1 > x 2 sin x 1 > sin x 2 if π 2 x 1 < π 2 x 2 x \in [0, \pi]\quad \Rightarrow \begin{cases} \cos{x_1} < \cos{x_2} & \text{if } x_1 > x_2 \\ \sin{x_1} > \sin{x_2} & \text{if } |\frac{\pi}{2} - x_1| < |\frac{\pi}{2} - x_2| \end{cases}

Therefore, the answer is F F T T \boxed{FFTT} .

Moderator note:

Can you solve this question without using the fact that 1 radian is approximately 60 degrees?

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