Question

find the value of sin (-750) and sec 25$\pi$ /8class 11 trigonometry question plz answer only if you are sure

Answer 1

sin(-x) = -sinx5

So, sin (-750) = - sin(750)

Now apply reduction formula.

By substracting 360 or its multiples from an angle, function remains same. Formula applied here is:

sinx = sin[x - (2×360)]

-sin(750) = - sin(750 - 720)

= - sin (30) = -1/2

$sin ( \frac{25\pi }{8} ) = sin (\frac{25\pi }{8} - 4\pi )$= $sin (\frac{\pi }{8})$

Now we know, cos2x = 1 - 2sin²x

So, sin x = $\sqrt{\frac{1-cos2x}{2} }$

$sin (\frac{\pi }{8})$ = $\sqrt{\frac{1-cos(\frac{\pi}{4})}{2} }$

= $\sqrt{\frac{1-\frac{1}{\sqrt2}}{2}}$

=$\sqrt{\frac{2-\sqrt{2}}{2} } }$

$sin ( \frac{25\pi }{8} )$ = $\sqrt{\frac{2-\sqrt{2}}{2} } }$

Answer 2

Answer:

Step-by-step explanation: