c3 help trigonometry URGENT

Original post by Muttley79

OK now substitute in the values of cos and sin.

The usual approach is to start with the LHS and compare it with Rsin (theta + alpha) - see the examples just before the exercise.

sub in what? wheres the cos and sin?

Reply 7

Original post by JSM1

This is where i have got up to

Show that

\sqrt 2 \sin\theta \cos \frac \pi 4 = \sin\theta

, and similarly for the

\cos

term.

Reply 8

Original post by _gcx

Show that

\sqrt 2 \sin\theta \cos \frac \pi 4 = \sin\theta

, and similarly for the

\cos

term.

how?

Reply 9

Original post by JSM1

how?

What does

\cos \frac \pi 4

equal?

Reply 10

Original post by _gcx

What does

\cos \frac \pi 4

equal?

i dont know

Reply 11

Original post by JSM1

i dont know

Are you familiar with working with radians? If not, I'd recommend reviewing them for this topic. (pretty sure it's covered in C2 though?)

Reply 12

Original post by _gcx

Are you familiar with working with radians? If not, I'd recommend reviewing them for this topic. (pretty sure it's covered in C2 though?)

what do you do to work what it equals to?

Reply 13

Original post by _gcx

Are you familiar with working with radians? If not, I'd recommend reviewing them for this topic. (pretty sure it's covered in C2 though?)

what do you have to do?

Reply 14

Muttley79

Original post by JSM1

what do you have to do?

You should know the exact value of sin and cos (pi/4).

[Hint - in degrees it would be 45]

Reply 15

Original post by Muttley79

You should know the exact value of sin and cos (pi/4).

[Hint - in degrees it would be 45]

yes 45 degrees, then what? ms shows 1/root2. how did they get that?

Reply 16

Original post by JSM1

yes 45 degrees, then what? ms shows 1/root2. how did they get that?

You should be familiar with

\sin 45^\circ = \frac 1 {\sqrt 2}

at least.

Reply 17

simon0

I tend to remember these two useful triangles:

http://edtech2.boisestate.edu/smithm/Images/trigfunctions4.jpg

(Source: http://edtech2.boisestate.edu/smithm/506/trigfunctionslesson2.html ).

Reply 18