#How Do you solve (bi) is there a way to always solve these questions the mark scheme doesnt show

31 messages · Page 1 of 1 (latest)

craggy wave
#

You have the answer from a yea

#

If you notice, the equation in B is the same as a

#

So if you plug in your R formula from A into it

#

You’ll get H = 3 + 2(expansion from A)

#

Where theta = 0.5t

#

And then to find the max, your cos(0.5t + alpha) will be set to 1

#

So your max is H= 3 + 2R

#

Then to find the time at which this occurs

#

Set cos(0.5t + alpha) = 1 and solve for t

weary willow
craggy wave
#

A is 2sintheta - costheta

#

H = 3 + 4sin0.5t - 2cos0.5t

#

H = 3 + 2(2sin0.5t - cos0.5t)

#

Imagine 0.5t = theta

weary willow
#

ok i see it now

craggy wave
#

H = 3 + 2(2sintheta - costheta)

weary willow
#

so to solve the max point what do i do now

craggy wave
#

Alwasy in these trig Qs if they make you solve for the R formula you’ll use it later on

weary willow
#

ok

craggy wave
#

So 3 + 2R

weary willow
#

how do i solve cos(0.5t+alpha)

#

sorry cant believe im struggling with a one marker

craggy wave
#

Cos(0.5t + alpha) = 1

#

Take arccos of both sides

#

0.5t + alpha = 0

#

So 0.5t + alpha = 0,2pi

#

Then minus alpha

#

Divide by 0.5

#

t= (2pi - alpha)/0.5

#

You ignore the 0 as you can’t have a negative time