solving trigo without calculator

**helloying** · June 27th 2009, 12:45 AM

Evaluate without the use of calculator, $\sin [ \cos^{-1} (1/2) + \sin^{-1} (4/5) ]$

**CaptainBlack** · June 27th 2009, 01:39 AM

Originally Posted by helloying

Evaluate without the use of calculator, $\sin [ \cos^{-1} (1/2) + \sin^{-1} (4/5) ]$

$\cos(\pi/3)=1/2$ (that's cos of 60 degrees, you are supposed to know this)

If $\theta=\arcsin(4/5)$ then $\sin(\theta)=4/5$ and $\cos(\theta)=3/5$ (think 3-4-5 triangle)

So new you want to know:

$\sin [ \pi/3 + \theta ]$

and you should be able to find this using the usual trig identity for the sine of a sum.

CB

Thread: solving trigo without calculator

LinkBack

Thread Tools

Display

solving trigo without calculator

Similar Math Help Forum Discussions

Help required on solving Trigo sum..

trigo solving

solving trigo equation

Solving trigo

strange problem in my calculator while performing trigo-function

Search Tags