find the value of sin, cosine, tangent using these double angle identities. please check if my equation is correct.

cos 2A = 1-2sin^2A
then it will be

Question

find the value of sin, cosine, tangent using these double angle identities. please check if my equation is correct.

cos 2A = 1-2sin^2A
then it will be

moongazer · Answer

$$sinA = \sqrt{(1-\cos2A)/2}$$

moongazer · Answer

and$$\cos2A = 2\cos ^{2}A-1$$
will be$$cosA = \sqrt{(\cos2A+1)/2}$$

asnaseer · Answer

correct so far

moongazer · Answer

and
$$tanA = sinA/cosA$$
will be
$$\sqrt{(1-\cos2A)/(\cos2A-1} = tanA$$

asnaseer · Answer

you got the last one wrong

asnaseer · Answer

denominator should have a plus sign instead of a minus sign

asnaseer · Answer

you seem to be pretty good at them already - just follow your instinct and use logical steps

moongazer · Answer

and do you have some tips to give so that will help me master these equations?

asnaseer · Answer

you don't need to remember all the equations. as long as you know the basic relationships, you should be able to derive all the rest.

moongazer · Answer

Actually, my teacher made the derivation I am just checking if I copied the correct one. :)
But i'll derive it myself later so that I can practice. Thanks!

asnaseer · Answer

yw